The Lead-Free Petrol Question
The following 3 part article first appeared in the journal of the Morgan Threewheeler Club in 1998 at the time that announcements were being made that that leaded fuels were to be phased out in the UK by the year 2000. The author, John Rowland, is a Development Chemist (Automotive) with Fuchs Lubricants (UK) plc, the manufacturer of Silkolene lubricants. John has kindly given his permission for his article to be re-published here, and supplied some added footnotes for non-British readers. He also passed on his thoughts on the subject now that leaded fuel has largely been withdrawn which I reproduce below:
"...nothing much has happened in the last 2 or 3 years which would require me to re-write the whole thing. I think some classic car owners have been panicked into fitting unnecessary (and possibly troublesome) valve seat inserts when LRP or a VSRA would have dealt with any potential problems.
As far as "T"-type MGs are concerned, all but supertuned racers will be more than adequately served by LRP 4 -star, or 95 octane lead free plus a VSRA.
Since I wrote these articles I have noticed some tendency to use lead-free fuel as an excuse, entirely unjustified, not to use old cars. The fact is, some owners do not really enjoy driving old cars, particularly when they are about as old as their vehicles! So, in the 1960s, they would say, "can’t get the tyres", in the 1970s " can’t get the spares", in the 1980s-90s "too valuable to risk taking it out .......and in 2000s "this lead free petrol will ruin the engine". Yet, strangely enough, the types who really want to use their cars seem to do so regardless of the obstacles. Certainly the fuel problem has not turned out to be the dreadful obstacle it was made out to be.
Yours sincerely
John Rowland"
Clifford F Knight -- 21 January 2001
The Lead-Free Petrol Question
The old vehicle movement is up in arms at the moment for fear that leaded fuel may soon be unavailable. In my opinion the problems associated with the phasing-out of 4-star have been exaggerated, and no engine will be at risk when running on "lead-free’ provided that a few simple precautions are observed and some obvious pitfalls avoided. I will attempt to justify this point of view later, but first of all in the interests of greater understanding, let us look at some ............
History
The United States Navy started it all back in the 1920s. Their ships did not run on gasoline but their carrier aircraft did, and getting airborne before the end of the runway prior to the invention of the steam catapult was vital! What they needed was more power, and one effective route to more powerful engines without weight or consumption penalties was to raise their compression ratios. But this caused detonation or pre-ignition which actually reduced power and damaged the engine. So the USN decided to look at the ignition quality of their fuel. Nobody had heard of Octane Rating then, but in modern terms Nineteen-Twenties aviation fuel was about 75 octane. They eventually tried a dash of a clear, heavy liquid which looked like dry-cleaning fluid; it was called tetra ethyl lead or TEL. This allowed much higher compression ratios such that the power of their air-cooled radials with some essential modifications went up from 450 BHP to 600 or more.
Essential modifications.... that sounds rather ominous, doesn’t it? Quite right. When the TEL had done its trick of delaying premature explosion (yes, that old problem) of the air/fuel mixture, the left-overs were rather nasty. This was all due to....
Chemistry
How does TEL prevent detonation? The best theory so far depends upon the "mirror effect" of lead oxide. When fuel burns, a flame front is supposed to advance from the spark plug in a fairly orderly fashion. Unfortunately radiation from this flame front into the unburnt mixture can raise its temperature enough to initiate sudden detonation, giving an explosive shock wave which hammers the piston, hence the well-known" pinking" noise. If there is some TEL in the fuel, it decomposes at the flame front to leave a fog of lead oxide dust, which reflects much of the heat back into the burnt gas. Consequently, high compression ratios which cause high gas temperatures before ignition can be tolerated. So far so good, but what happens to all this lead oxide? A lot goes out through the exhaust, corroding the exhaust valve on the way. Some remains in the combustion chamber forming an orange-brown stony deposit which masks the inlet valve and acts as a "glo-plug’ causing pre-ignition and runnin g-on. Even worse, some unwanted metallic lead is also formed which tries to alloy with any hot metal it can find. In the early days it also dissolved the mica insulation on 1920s spark plugs. Metallic lead, or any other metal does not raise octane numbers or stop pre-ignition, thus giving the lie to miscellaneous silly ideas involving lead shot in the fuel tank or tin pellets in the fuel line.
So valuable, however, was the prize of greater efficiency and power output that the chemists persevered with TEL and dealt with the side effects as best they could. Their first move was to use a chemical "eliminator’ to sweep the lead oxide and lead out of the combustion chambers in a less corrosive form. Soluble bromine compounds worked very well; chlorinated ones rather less so, but these were cheaper. Ethylene dibromide, a volatile liquid once used as a local anesthetic was added to the petrol along with the TEL. After the lead oxide had done its radiation-reflecting job, it reacted with the bromine compound to form a white crystalline salt, lead bromide. This melted at a relatively low 370 degrees Centigrade, much lower than the 9000C for the common form of lead oxide, so it was blown out of the combustion chambers on the exhaust stroke as a white vapour. And guess what? This liquid salt behaved as a lubricant on its way out and virtually eliminated valve seat wear. Now that was a bonu s nobody expected! The cheaper chloride eliminators, still used today with the bromide type are not quite so good because lead chloride melts at 5000C, and can accumulate in a cool-running engine. This is why a good motorway thrash would often rejuvenate an engine which has been used just for pottering off to the shops back in the days of high lead fuel. It was all a matter of melting off the lead bromide/chloride salts! (Bromide/chloride mixtures are often referred to as "lead halides"). So the white coating in the exhaust tailpipe after the aforementioned thrash using the old pre-1986 high-lead 4-star was due to lead halides. Are you interested in old piston-engined aircraft? The immaculate Spitfires and Mustangs at airshows are cleaned too often, but should you happen to see any original colour photos of operational wartime planes, you will see creamy-white streaks leading from the exhaust stubs. This is lead halide. "Avgas" in those days were stuffed with TEL to the tune of several grams per gallon, so massive doses of bromide and chloride were needed to get rid of it. Just one Merlin engine would pump out several pounds of lead halides on a sortie to Berlin; almost chemical warfare!
It has been stated in the 1991 VSCC paper on valve seat recession (recently re-issued by the FBHVC) that lead oxide and lead sulphate are responsible for preventing valve seat recession. This is not entirely correct. The copious amounts of lead halide vapour released by burning petrol do the lion’s share of the job.
May I stop here and digress for a moment?
You, the reader, having ploughed through all this stuff about lead bromide and so on, now belong to an elite! For every million drivers who have heard about lead in fuel, perhaps a thousand know about tetra ethyl lead or the similar tetra methyl lead. Of that thousand, perhaps four or five know that it actually emerges from the engine as lead halides. Prominent among the multitudes that do not know are all those media mega-mouths who are fond of sounding off about lead in the environment. There is virtually no lead in the environment that originates from petrol; only lead salts. This is not hair-splitting. They are very definitely not the same thing. Crucially, these lead salts are water soluble, and are therefore much less harmful environmentally than pure lead.
True, lead halides are poisonous and reducing their emission levels is a good thing, but it is also true that all but a tiny fraction of those millions of tons of lead salts scattered over Europe in the last sixty years have now been washed into the sea. If
large amounts of metallic lead or lead oxide had been involved they would still be sitting there in soil and water working their way into the food chains just as lead from old plumbing and shot-gun cartridges does. It is worth remembering that lead weights from anglers’ lines have killed hundreds of swans on Britain’s rivers; residues from petrol have probably not harmed a single one.
Metallurgy
To get back to the subject, using lead oxide eliminators did not solve all the problems, but the chemists had done their bit. The rest was up to metallurgy.
Because of TEL, metallurgists concentrated on valves rather than valve seats from 1930 onwards. Of course, inserted valve seats were used in OHV engines with aluminium heads, but these were not necessarily hardened. Low-alloy steel valves, especially exhausts were corroded very badly, such that an engine could die after only a few hours of high-speed use on leaded or "ethylised" fuel. Even so, run of the mill motors were made with nonresistant valves well into the 1940s in spite of leaded fuels such as Pratts Ethyl being available from a surprisingly early date. (According to the VSCCs excellent 1991 report on valve seat recession, leaded petrol first appeared in the UK in 1927).
The first reference to using leaded petrol in Morgan 3-wheelers appears in that valuable little book published by Maskell for Morgans Ltd in the late thirties. It recommends as follows for the special high-compression Matchless MX2 and MX4 engines fitted with 7.5:1 pistons:
"Suitable fuel should be used for this ratio, ie. 50% Benzole and 50% No. 1 Petrol. Ethylised fuels will suffice, provided prolonged high speeds are not required".
So lead-free fuel was actually recommended for high speed use, very much the opposite to current practice. I think it was the lesser of two evils. The "ethylised" fuel may have protected the valve seats, but it would have rotted the exhaust valves, probably made of low-alloy chrome/silicon steel. On the other hand, the lead-free "racing-mix’, probably about 90 octane, would have looked after the valves when they were red-hot under full power, even though the valve seats may have suffered. In practice of course, there was little opportunity then for "prolonged high speeds", especially as the only motorway in the British Isles was a closed loop on the outskirts of Weybridge! Also, it is essential to realise that nobody expected valves or anything else to last for years. The same booklet suggests decarbonising at 2000 mile intervals, and valve regrinds every 4000 miles. Most owners were happy to see 20,000 miles before the engine was scrapped or rebuilt from top to bottom, so valve se at recession did not really get chance to become a problem. It is
certainly not something that has suddenly appeared; it has more to do with the modern motorist’s expectations of engine life and attitude to servicing.
The 1991 VSCC report has shown that American engineers were well aware of valve seat recession and the reasons for it nearly eighty years ago. The reason the USA ran into trouble first was because their engines did get used for "prolonged high speeds", and that, as Mr Maskell also realised, was at the root of the problem.
The modern engine which hangs together for 100,000 miles with no major servicing is the result of years of design effort, and research into metals, fuels and lubricants. Unfortunately, the driver of a modern car who compensates for its yawn-inducing blandness by owning a vintage or classic machine tends to expect the same life from an old-technology engine. This is not being fair, although modern spares made from better quality materials plus modern lubricants do give much more life and reliability than pre-war driver could expect. When anyone utters the dreaded cliché "They don’t make ‘em like they used to do" over my Matchless-engined Morgan I always reply "No, they wouldn’t dare!" The fact is, old engines wear out, and even major components such as blocks and crankcases eventually have to be replaced. It is no good blaming everything on the government or the petrol companies for withdrawing leaded petrol!
Back in the 1930s metallurgists were sowing the seeds which produced the modern engine by much improving valve life, even where leaded fuel was used. British aero engines in WWll used the famous Jessops KE965, a reliable chrome/nickel non-magnetic stainless steel, capable of resisting the very high lead levels needed to produce octane ratings as high as 130. Its present-day equivalent is 21-4N and its derivatives, used in almost all petrol engines for inlets and exhausts. Earlier engines even into the 1970s would usually have cheaper Silchrome inlet valves, hence the importance of not mixing them up when stripping cylinder heads. 21-4N is 21% chromium, 4% nickel, the rest being mainly iron. Even fancier alloys have been used. In the late fifties the Manx Norton and its close relative the Vanwall racing car used valves made from an iron-free alloy used in jet engines known as Nimonic 80A. This was very heat resistant, but suffered worse lead corrosion than the cheaper high-chrome stainless steels, so it did not catch on.
To conserve precious nickel and chromium, the famous wartime jeep, intended to run on low-octane lead-free army petrol, did not have lead-resistant valves. A certain dispatch rider, none other than the late, great Dennis Rogers of the MTWC "acquired" some aviation petrol for unofficial jeep trips during the Italian campaign. For a week or so the Sherwood Foresters’ jeeps went like rockets. The week after they didn’t go at all!
Valve Seat Recession:
The Size of The Problem and What To Do About It.
But first......a word from our historian
The valve seat protecting trick of lead halides has of late rather obscured the fact that TEL was and is primarily an octane improver. Particularly during and after WW II, crafty refining techniques such as catalytic cracking and alkylation raised the anti-knock quality of the basic fuel so less TEL was needed to reach a particular octane number. Also, as the years went by more octane improvers were discovered. Some were a disaster. Soluble iron compounds such as ferrocene were even more effective than lead, but the residue after combustion was jeweller’s rouge! (Red iron oxide). The effect of this on piston rings and bores can be imagined. Another one based on manganese worked well, and was used together with TEL for a while in the USA, but poor stability (it formed brown filter-blocking sludge) killed that one. Well, it should have done, but I recently (Jul 1998) tested two commerciaI octane boosters selling in Italy under well-known brand names that were based on manganese, Personally, I wouldn’t touch ’em with a 2-speeder starting handle!’ But other lead-free octane improvers worked by modifying the combustion process, not by the "oxide mirror" effect, and these left no residues that needed eliminating, consequently doing valve seats no favours at all. These are now widely used, and together with improved refinery processes actually made high octane "lead-free" a commercial possibility by the early 1970s. So please do not knock lead-free. Between the 60-ish octane lead-free of the 1920s to 98 Super Unleaded of today there is seventy years of R and D plus a war!
OK, where does this leave the vintage engine?
This fancy lead free fuel is not going to help really old veteran/Edwardian/early vintage engines, but it will not do them much harm either. As their compression ratios are usually around 4:1 and lubrication total loss, valve seat wear was very low on their original primitive lead-free because valve temperatures were far below the cherry red 6000C of the modern hot-shot motor. This is still true for the current 95 octane lead free. The heavy carbon residues from old-fashioned heavy monograde non-detergent oil being used at 200 miles to the pint helped to protect valve seats; the engines simply never got hot enough to burn it off. So I am told, valve clearances could actually increase due to "valve seat progression"; the carbon lifted the valves off their seats! The downside of this was, of course, the regular chore of de-coking.
In my opinion the typical low-rewing pre-1925 motor producing 15to 25BHP per litre such as a JAP KT or KTW V-twin has nothing to fear from lead-free fuel. True, modern oils, detergents in the fuel, and replacement pistons with oil-control rings that actually work mean that protective carbon residues are reduced, but the calcium and zinc-containing left-overs from burnt modern oil are also effective valve seat protectors. The cautious owner will do no harm, and achieve the always desirable belt-and-braces effect by adding a little oil to the fuel, or even one of the VSRA (Valve Seat Recession Additive) products which are becoming available. (More later on these). Incidentally, when I mentioned "oil" I did not mean that useless, overpriced (and usually red) stuff known as upper cylinder lubricant. 2-stroke oil is much better! Used at about 5ccs per litre of petrol, in a low compression engine it will leave some carbon on the exhaust valve seats and help to look after the internals, especia lly among the 500 miles-a-year brigade where the engine is more likely to expire from rust and cobwebs than valve seat recession! So, oddly enough, it is the engines produced furthest from the brave new Millennium which should clatter into it with the least trouble.
I did say that modern lead-free would do old engines no harm, and I stand by that, but some VSCC members would not agree. Readers may remember a VSCC fuss years ago, well before the valve seat panic, concerning the octane requirements of some 1920s engines. Apparently, these motors were not happy with high octane fuel of any kind, suffering from overheating, low power, and poor sensitivity to ignition advance. (Oddly enough, there were no published complaints from the VMCC). To cut a very long story short, the conclusion reached was that modern fuel burned too slowly, and an octane reducer was needed. The one chosen was paraffin (kerosene), and a surprisingly compliant Customs and Excise gave the VSCC a legal OK to dose their petrol with this duty-free fuel. Personally, if faced with this problem, and it could perhaps affect low compression liquid-cooled side-valves such as the Matchless MX, I would not choose paraffin. Unless used with a heated manifold Ferguson tractor style, it will not volatalis e, washes the oil film off the cylinder walls and contaminates the oil. A much better octane reducer is "heptane fraction", a cheap volatile industrial solvent very similar to lead-free petrol, except that the octane rating is about 10! (Very pure n-heptane is used to set up octane test engines for the "zero octane" reading). If anyone has run into this problem with modern fuels, I can put them in touch with an industrial solvent supplier, should they wish to try this slightly illegal solution. One pint to every gallon of 95 octane should drop the octane number to around 85.
The way different hydrocarbons choose to burn in a spark-ignition engine is a very mysterious business. It is well known that the term "100 octane" means that a fuel has the same knock resistance as pure 100% octane when run under controlled conditions in a weird variable-compression single cylinder "Co-operative Fuels Research" (CFR) engine. (Believe me, this gadget bears very little resemblance to any car or motorcycle engine!). But it has to be the right 8-carbon compound, known as iso-octane, with 5 carbon atoms down the middle and the other three sticking out of this backbone at positions 2 and 4! If it is the straight chain n-octane with exactly the same chemical composition, but 8 carbons all in a row, the octane number of this variant is only 25! As mentioned above, the straight chain 7-carbon n-heptane is used as the calibrator for zero. So an "80 octane" fuel gives the same result, ie. knocks at the same compression ratio, as a blend of 80% iso-octane 20% n-heptane. Have you got that? It is not the end of the story, but I’ve got away with this irrelevant digression for too long as it is, so back to the subject.
The situation for late vintage and pre-War engines
It is all really down to compression ratios, engine revolutions and power output. The higher these go, the hotter the valves, and the higher the seating pressure on the valve seats. (A fast-running engine with valve overlap needs strong springs to close the valves, particularly in a pushrod OHV design). Around 6:1 for air-cooled, and 7:1 compression for a liquid cooled motor, combustion chambers are too hot for carbon to exist in a well driven (ie. fast!) vehicle with a correctly set up carburettor. The twostroke oil in the petrol trick will help, but for engines covering reasonable mileages the only effective remedy when 4-star finally goes is a VSRA. Effective valve seat recession additives do exist. They are based on fuel soluble compounds known as sodium (or potassium) sulphonates. These have no octane-improving effect, but they do decompose during combustion to sodium/potassium sulphates and carbonates, which protect valve seats as molten salts, analogous to the action of lead halides arisi ng from leaded fuel. They are fairly effective down to 100 parts per million (0.01 % or 1cc to ten litres) and very effective at 400ppm. They are not expensive and they are backed by a considerable amount of R & D carried out by reputable Companies such as BP and the Lubrizol Corporation. One particular potassium-based version I have used myself is made (but not retailed) by the chemical side of BP, and is backed by about forty pages of comprehensive test results. If anyone is really keen I can send a copy, but just to give everyone an idea of the work done, tests on 1.2 litre Opel Kadett engines (apparently very prone to seat recession) were run for up to 60 hours at 4000 RPM, maximum torque, which is equivalent to 60 hours going flat out up a hill, I suppose! Seat recession after 20 hours (on a new engine, of course) was 0.3mm, which stayed more or less unchanged for another forty hours. (This was a 440 ppm treat rate). Other tests included 28 different makes of car, covering about half a million kilo metres using the VSRA. Of course, the Opel engine and all the others were by our standards modern designs running high compressions and far more at risk than any pre-War (or even pre1955) engine. I am convinced that any Morgan 3-wheeler engine, Matchless, Ford JAP or what have you, will come to no harm with a shot of VSRA in the fuel. Unlike the Pill, you can even miss a dose or two without panicking: the residue from the last shot will see the valve seats OK!
These VSRA’s should not retail at a high price. Although fuel additives carry duty, sufficient additive to treat up to 500 litres of fuel should cost less than £10. Do not be deceived into spending vast sums on some apparently super-amazing product; these are always overpriced rip-offs. This means that treatment costs will be around 2 to 4 pence per litre less in fact than the current price difference between standard unleaded and 4-star. Bearing in mind that hardened valve seat inserts are not only expensive but often impossible or risky to fit to many old engines, VSRAs provide a very practical alternative. However, there are only these two solutions; to date, nothing else will work.
Understandably, some moderately intelligent people (such as civil servants) have been fooled into endorsing the totally useless "tin pellets in the fuel" idea. This is due to the "Elephant effect". You know the old joke: Driver on the Ml throws balls of screwed-up newspaper out of the window every few miles. Passenger queries this. Driver says, "It keeps the elephants off the central reservation". Passenger: "But there ain’t no elephants..." Driver: "I know! pretty effective, eh?"
In other words, any solution solves a non-existent problem, and in old engines which have run for years on 4-star, with valve seats furred up and work-hardened, it will take years of pottering about on lead free for seat recession to get started, so its understandable how quack remedies appear to work sometimes.
I did meet the inventor of one version of the tin alloy pellet about 15 years ago. His "reasoning" and proof contrast nicely with the BP work mentioned above. This engagingly loopy South African engineer turned up at my place of work, Silkolene Lubricants, trying to sell his idea. Essentially, his proof consisted of various stories which boiled down to "old so-and-so tried them and said he noticed a difference". In those days, the pitch was reduced wear, lower fuel consumption etc., with no mention of valve seat recession, so presumably this benefit appeared later. He did not know the correct meaning of the word "catalyst", and seemed to think the difference between metallic tin or lead, and fuel soluble organometallics such as TEL or tin carbonyl either didn’t exist or was of no consequence. The invention story was pure myth. (Complete sincerity and false memory syndrome are compatible). Apparently, he helped the Russians during the War cure pre-ignition problems on RR Merlin s by passing their "poor quality" fuel through packs of tin pellets. This was in spite of the Russians having an excellent oil industry dating back to 1890, they were completely up-to-date on TEL and octane rating, they made some good in-line and radial engines, which they operated at low altitude where high octane fuel is essential, and their national character was not exactly sympathetic to foreigners trying to tell them their business. The moral is, caveat emptor! When there is a problem concerning motor cars some odd characters appear with miscellaneous totally daft remedies lacking any sound test data, and all of them are convinced they are going to confound the established oil and fuel companies and take the world by storm.
The class of engine most at risk is the post-War high compression, high revving type that needs valve seat protection and an octane rating of 95 or higher. This more or less rules cut anything fitted to a Morgan, except for the odd seriously tuned Ford. I used to use the old 92 octane leaded 2-star in my 7:1 MX4, which could give rise to incredulity:-
Attendant: "You’re not putting 2-star in that, are you?"
JR: "I’ve got to. They don’t make none-star anymore!"
I suppose this more or less wraps it up as far as the Morgan tricycle is concerned, and I hope a few minds have been both put to rest and stimulated.
But! I’ve got lots more to say (who would have thought it?) concerning post Morgan vehicles, which many of us also drive, with some attempts at Millennial crystalgazing and various inflammatory political remarks, all in the best tradition of the MTWC!
A Final Word
It’s Alright For Some
Are you fed up with all the restrictions, rules and regulations, taxes and tin boxes which make classic and vintage motoring less of a pleasure? Would you like to travel without let or hindrance, speeding along at any speed you fancy above 70mph, burning high octane petrol with a massive lead content and low tax, scattering lead halides to the four winds without a catalyst box or even a silencer to get in the way? OK, you may be saying, take me to your time machine. But I do not need anything so esoteric. All I need is .... a small aeroplane. Yes, the universal standard 100LL Avgas used in all piston-engined aircraft except microlites has a high TEL content, equivalent to 0.4gm/litre of lead, over twice that of 4-star, and it carries a lower rate of tax. And when is this due to be banned or phased out, you may ask. Well, as far as I am aware, not until the year 3000, or until such time as some amazing power source knocks the IC engine off its perch. (Which will not happen for a very long time!). Thi s is why the petrol companies can pledge to supply small quantities of 4-star "indefinitely", because the resources to synthesise TEL, and blend it with bromides and petrol feedstocks will remain in place as long as aviation piston engines requiring high octane fuel are being made and used. This will be for at least fifty years, because aircraft engines higher in power than simple ‘microlite" units, such as the Lycoming and Continental are being manufactured at this very minute, and they will need leaded fuel for their entire working life. Furthermore, the typical aviation motor is a long-lived device which puts in a very good innings before it collects its bus pass!
I am sure many of you are wondering why these aviation outfits, who always claim to be so technically advanced cannot get their act together, fit hardened valve seats, and tweak their engines to run on lead-free just like the downtrodden car manufacturers. Unfortunately, the answers involve another look at the octane number test method.
Nothing is simple!
Look closely at any privilege and a dual standard will pop up somewhere. The octane number method for car engine petrol has the plebeian name of RON. It would be fitting if the aircraft method was called ETH (hands up all 1950s radio fans), but it is in fact the Geordie expression MON.
The MON (Motor Octane Number) method was first mon, and defined how the variable-compression test engine was set up and operated. (This was in the late 1930s). As explained in Part 2 of this rambling epic, the pure hydrocarbon fuels
n-heptane and iso-octane were used to define zero and 100, and the test fuel fell somewhere in-between. Lead-free petrols were between 60 and 75 (MON) octane, and even a hefty dose of TEL could only bring the number up to 90 in any fuel which could be made in quantity at a reasonable cost. (The Battle of Britain was fought on 90 octane aviation fuel. Lower forms of winged life such as Tiger Moths and Ansons had to make do with 75 octane lead-free).
Later, the Americans decided that the MON method did not tackle car-orientated fuel problems such as running-on, so the Research Octane Method (RON) was developed, involving the same test engine run at a lower speed and temperature. The same set-up fuels are used, but this less severe regime gives a much higher octane number for most petrols. This is the number quoted on all petrol pumps selling taxed road fuel in Britain, other EEC countries and most of the rest of the world. However, by aviation standards even Super grade (98 RON) is pretty poor stuff. Here is an extract from a recent BP data sheet for BS7070~ unleaded fuels:
Grade Premium Super-Green
RON, minimum 95 98
MON, minimum 85 87
Total Lead g/lit (max.) 0.013 0.013
Yes, "unleaded" is allowed to contain a small amount of lead, but the true figure in practice is very much lower than the " back-covering" figure quoted above. If recent (June 98) proposals for World-wide fuel standards go through, even this permitted lead level will be replaced by "below detectable amount" which in practical terms means below one part per million. Interestingly, these world-wide standards include a 91 RON/82 MON fuel. If this becomes available I will be there with my Super Sports, in the queue with the Tiger Moths!
100LL Avgas, as its name suggests is a 100-octane fuel, rated by the severe MON method. The easy-going RON would award it about 108 to 110 octane points, making it "Nine-Star" to us poor peasants who drive cars. This is why aircraft piston engines cannot afford to go lead-free. Being mainly aluminium, they already have valve seat inserts, but that is irrelevant; re-designs to deal with a drop of 13 MON points (ie. from 100LL to 87 MON/98 RON Super Unleaded) would result in larger, heavier low-compression engines using more fuel for less power.
Incidentally, the letters "LL" mean "low-lead", because back in the 1960s 100LL was low lead compared with other aviation fuels which could contain up to 1 g/litre; by the standards of the 1990s it is very high lead, but it is still called low-lead. (Has everyone got that?) The Avgas specification allows it to contain up to a massive 0.86g/litre of lead, but in practice the actual content is 0.4g/litre.
Avgas can be purchased by anyone. Many small airfields will willingly sell a few gallons, and in the 1980s it was common for motorcycle road racers to use a 50:50 mix of Avgas and 4-star, giving a fuel with a RON of about 104. The ACU and FIA put a stop to this in the early 1990s, but a lot of it still goes on at the enthusiast level, in sprinting, drag racing and so forth. Contrary to popular belief, Avgas is not any more dangerous than ordinary petrol. Due to its low volatility (vapour locks at 12,000 feet are not appreciated) it is less likely to catch fire than standard lead-free, and it
can be used in high-compression car and motorcycle engines. The only problem is likely to be poor cold starting; aircraft engines have carburettor heaters.
Multiple Solutions for the Classic Engine
Far from being condemned to a museum after 2000, the highly tuned classic that requires high octane leaded fuel presents its owner with the luxury of several solutions.
The easiest choice is to use Super unleaded with an effective VSRA. This is what I intend to do for the tuned 948cc A-Series engine in my MK I Sprite. As I am one of those irresponsible people who thrash small engines to within an inch of their life, I shall use double the recommended minimum dose! For larger, lazier engines of 2 litres or more capacity there will be no need to do this for road use except for those determined to lose their licence.
If 98 octane unleaded becomes scarce there are such things as octane boosters to use with normal unleaded, but the only safe ones (for engines and people) that also work are those based on MTBE (methyl tertiary butyl ether). This does not, of course, leave any deposits on valve seats so it must be used with a VSRA. For die-hards or classic racers, there will be some leaded 4-star available. Apparently, the petrol suppliers will turn out 0.5 percent of total petrol production, which doesn’t seem much, but it amounts to a surprising 111,260 metric tons or about 34 million gallons, enough to drown every D-type Jag and AC Cobra in the British Isles, I should think! (1997 UK petrol consumption was 22,252,000 metric tons of which 6,138,000 was leaded 4-star). In the UK small private aircraft are relatively uncommon compared with other European countries, so Avgas consumption is a mere 33,000 metric tons or about ten million gallons; about a third of the permitted 4-star production, but requiring a similar quanti ty of TEL. (I wonder if this is really a coincidence?) Obviously, the big problem will be finding a 4-star pump. I expect they will be confined to race tracks or a few specialist garages, and the price tag will be around 90p per litre. Even so, lead halide residues are persistent, so the odd tankful between doses of Super Unleaded will suffice. Indeed, the 0.1 5g/litre of lead is more than enough to protect even the most fragile valve seat. Accordingly to some careful work done in the USA, the minimum lead content necessary to provide valve seat protection for most engines is 0.026g/Iitre, only one fifth of the current 4-star level, although Rover recommend 0.06g/litre for their A-Series engine.
Obviously, the people using the six million tons (1.8 billion gallons!) of 4-star are soon going to mop up the mere 34 million gallons per annum of "permitted" fuel after 2000, so the "leaded" pump on 99 percent of forecourts will go. To replace it there will be a British Standard lead-free 4-star, probably containing a minimum quantity of VSRA. (Larger doses can affect exhaust catalysts and some types can corrode turbo charger impellers). At the moment, there is no official definition for this grade, but it is basically intended to keep late-model iron-head engines going until they die. Being a suspicious soul, I shall stick to 98 octane unleaded, and add a trusted VSRA.
The more perceptive among you will have noticed that Avgas is highly leaded, and it will work in an ordinary engine. So what happens if, shall we say, 10 percent of
100LL is added to 98 RON unleaded? The result is a 99 octane petrol with at least 0.04g/litre of lead,sufficient to look after virtually all valve seats even under race conditions. This is in fact quite legal for off-highway motoring, but not so for road use, because there is lower duty on Avgas aviation fuel, and non aat all on aviation jet fuel. (There jolly well ought to be, because it is a proven but unpublicised fact that jet aircraft contribute far more to atmospheric pollution than road transport does, but that’s another story). So now I’ve told you that a shot of Avgas will put some lead in your ...... er, tank, you must all promise not to do it, OK?
Speaking of stories, here is another one. (I’ve stuck to the subject for long enough). Very high octane petrol is possible because of a Great British Invention. This took place in 1938, that valuable year won by that under-rated PM Mr Chamberlain. A couple of very bright chaps at the Anglo-Iranian (BP) oil refinery labs. at Sunbury were asked by their boss, who had Rolls-Royce contacts, to have a go at producing a fuel using refinery gases which would have a high content of iso-octane and other "high octane" molecules. (The iso-octane for the test engines was produced in gallon batches at huge cost by a tedious laboratory method). So, after much theorising, they spent a Saturday morning when the lab. was quiet passing two types of gas through a flask of chilled sulphuric acid. It worked first time. The resulting fluid, called "alkylate" only needed a moderate dose of TEL to reach 100 MON. Nine months later a pilot plant at Aberdan (in Iran) was on stream, and Mr Stanley Hooker of Rolls Royce, working in a dispersal office at the Silkolene factory here at Belper ..... I had to mention that ..... had tweaked the Merlin up to 1400 BHP using the new fuel. In early 1941 the RAF started taking delivery, replacing the 90 octane leaded with 100 octane, and later moving to even higher numbers for some engines. But alkylate is still an expensive fraction, which explains why the current 100LL is quite pricey even with the lower tax
After all this fuss, has lead pollution gone down?
The whole point of reducing or eliminating lead in fuel was to reduce lead levels in blood, particularly in children, where high lead levels had been linked with learning difficulties and low IQ. There was much controversy over the amount that was "safe", one report (DHSS 1980) claiming that any level below 35 micro-grams per 100ccs of blood was OK, whilst another (Yule-Lansdown, 1981’) quoted firm evidence that anything above 12 micrograms caused measurable problems. Perhaps as a result, lead in road vehicle petrol was dropped from 0.4 to 0.15g/litre in 1985. (a microgram is a millionth of a gram)
This has had a very distinct effect. According to "New Scientist" (11July98) lead levels in blood are now down to one third of those measured in 1987. The article concluded that these results vindicate "earlier measures to remove lead from petrol, paint, solder and food cans". (Notice that a level-headed scientific journal, unlike trend-chasing newspapers or puritanical environmental loonies does not blame petrol alone). It goes on to say that "there are still risks from flaking paintwork dating from the 1960s and from soft water fed into homes through vintage lead pipes". Yes, lead is always with us in some form or other, emphasising that a witch-hunt against a very limited supply of leaded fuel for classic cars and aircraft would be merely vindictive and serve no environmental purpose. In the north of Derbyshire lead ore waste has been scattered about for almost 2000 years, and in houses built of (or on) granite the dangerous gas radon seeping out of the stone decomposes t o fine radioactive lead dust. That convenient scapegoat the motor car was not, and never will be entirely to blame.
Does anyone need to feel guilty?
Among the vintage/classic vehicle movement, certainly not. It would take a whole season of classic racing to equal the effect of just one Piper Aztec taking a load of grouse shooters from London to Scotland. Worse that the high lead Avgas, the lead pellets scattered over acid peat moors feed lead into the environment for many years. Across Europe, lead "emissions" from sporting guns amount to 30,000 tons every year.
Old cars are generally well-liked and my personal feeling is that there will be no moves to restrict their use to any greater extent than those already operating on all cars. When I first got interested in Morgans and so on in the 1960s, there was a widely-held view that a brave new motoring world would have no place for old machinery. There were responsible people around then who really believed that the year 2000 would see turbine-powered projectiles hurtling from one glittering high-rise city to the next, following buried wires and keeping station by radar! In fact, the likes of S.F. Edge, C.S. Rolls or Madame du Gast would find the controls of any modern car familiar, and would be hogging the outside lane in a Blandeo within hours of being let loose. In spite of their apparent lack of safety features, old vehicles do not have, or cause, many accidents, as the low insurance premiums testify, but we must all keep up the public relations side. Anyone who expresses any interest in my Super Sports gets offe red a ride. A surprising number accept!
There are many unpublicised reasons why the modern aeroplane and car are more polluting than is commonly admitted. (Guess who keeps a file on this subject!) Equally, there are reasons why old vehicles are greener than they look. Here is just one example.
Far from being primitive, many old cars include a marvellous composite material in their construction. This light, rigid and biodegradable substance really does grow on trees! Unlike carbon fibre, kevlar or plastics which consume vast amounts of energy and raw materials, and generate assorted greenhouse gases during their production, wood actually contains atmospheric carbon dioxide. (Remember all that photosynthesis business?). So any wood-framed car is keeping greenhouse gas out of the atmosphere. The 60kg of wood in my Morgan contains about 25kg of carbon which originally came from fifty cubic metres of carbon dioxide greenhouse gas, quietly incorporated into the structure of ash and birch trees many years ago. The calculation is simple - please get in touch if you want to know the details. If you merely want an answer, multiply the weight of your wooden body frame, Mosquito fuselage, boat or whatever (in kilograms) by this fiddle factor: 0.833. The answer will be in cubic metres at 20ºC and 1 b ar pressure.
I expect the modern Morgan Plus 8 could claim about 150 cubic metres of greenhouse gas in the bodywork. (Is that about right, Mr Morgan?). More to the point, it is not assembled by power-hungry robots. Some of the carbon dioxide emissions from that establishment on Pickersleigh Road come from certain inhabitants of Malvern, burning off their cornf lakes and bacon butties as they bash panels or stitch upholstery.
The message could not be clearer: Save The Planet Drive a Morgan!
JOHN ROWLAND
26/10/98