Unleaded Fuel Issues

FYI
Y'all
Taken From: http://www.jec.org.uk/fuel.htm

A Further Complication
Burlen Fuel Systems inform us that there is another potential problem to using unleaded fuel in engines not originally built to take it. This is the effect of the more "aggressive" nature of unleaded fuel on nitrile based "O" rings, diaphragms, seals and even rubber pipework in the fuel systems of many classic cars.

{Especially Lucas PI)

Apparently, the US market addressed this problem years ago and now Burlen have worked closely with them and SU and Zenith branded products, proving the suitability of various alternatives for use with unleaded fuel in the UK.

They can now supply all that is needed and for more information and advice it is best to contact them direct at Burlen Fuel Systems on 01722 412500.


(Sodium LRP has been reported to damage SAAB Turbo vanes in Sweden)

IanC

Thanks for that weycoil.

I have read of this phenomenon and as I recall in the mid eighties when unleaded appeared on these shores there were a number of burnt out Sierras at the sides of motorways.

Must check my MGB.

Cheers
Pete. ;)

Well we're only just catching up to 98 octane unleaded here, and then (so far) only in Victoria at Shell. But it should be spreading around the country this year.

I'm not sure its the octane rating. I think its the aromatics used in unleaded.

Elephino
I think you'll find that Unleaded is just that and there is NO tetraethyllead compounds of any sort in it.
The anti-knock properties are obtained by a mix of aromatics, including increasing the levels of Toluene (which I my opinion is worse than Pb)

Another snippet I remember reading somewhere is that when fuel was first made and you had to buy it from the Chemist in gallon jars, it was just a Heptane/Octane mix.

Lead was put in as the Oil companies reduced the quality of the fuel, to make more money out of it.
Thats not to say that a post-50s car woudl work on this fuel, but that the PB solution may have been driven by profit more than chemistry.

IanC

I was only pointing out how our fuel isn't so good, but actually it is partly octane rating that is not very good for cars designed to run on leaded fuel. As unleaded has a lower octane, it isn't as good as the leaded for which the car was designed (I think about 100 octane or so at the moment, I know it has gone down over the years). But it is not the only factor.

Don't forget that unleaded still has lead in it, just not as much as leaded.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by elephino:
I was only pointing out how our fuel isn't so good, but actually it is partly octane rating that is not very good for cars designed to run on leaded fuel. As unleaded has a lower octane, it isn't as good as the leaded for which the car was designed (I think about 100 octane or so at the moment, I know it has gone down over the years). But it is not the only factor.
<HR></BLOCKQUOTE>

I agree with you Mr E however I was thinking more of the aggressive nature of the constituents rather than the knocking effect caused by low octane levels. ;)

There was an article in the MG Car Club's mag last month which appered to suggest that leaded fuel caused damage to aircraft engines during the thirties and forties and so unleaded was developed to counter those problems. I will research that one. ;)

There is lead in unleaded. I know it is a very small amount, but it is there.

Hmmmmmmmmmmmmmmmmm. ;)

I think you'll find that there is a difference between the formulation and the legally required/allowable compositions.

In order to cope with inter-tank /cross contamination at the plant/distribution centre/pipes/tankers/retail outlet Unleaded is permitted to have up to about 3 part per million organo-Pb compound.

But it is not made with it in, as even these trace levels destroy the catalyst active zones.

:-)
IanC

Some forums get BUFFOONED!!!. We get BOFFINED!!!!! ;)

So I wasn't wrong...it's just I wasn't right either.

Believe I can give some more information, as gasoline and its components was my profession for some years. Unfortunately this cannot be explained in 3 sentences only.

First of all, Yelwoci is right concerning lead in gasoline. Official specification allows a small part of lead (ppm range) also in unleaded (therefore it’s called „unleaded“ and not „lead free“) which may be caused by switching between the systems. This means that small lead contamination m a y but not w i l l be there. As leaded more or less banned (here in Europe), such contamination is unlikely today.

Yelwoci is also partly right concerning the heptane-hexane mixture of the early days (19th century). Basically this stuff was „cleaning spirit“, called „Ligroin“, a low-boiling petroleum fraction, available from chemist shops and pharmacies in those days. The octane number was poorly low, about 50 to 60, but sufficient for engines revving not more than 1000 or so. The oil companies didn’t reduce the quality of the „fuel“, but they had been forced to make it available in commercial quantities to cover this new market. The straight-run refinery gasoline was a C5-C9 hydrocarbon mixture, not as clean as Ligroin, but much better suitable as engine fuel. The octane (RON) rating of this early real gasoline was about 60 to 80, so the „reduction of quality“ is wrong.
During the 20s and 30s engine revving increased to 3.500 or so, and the compression ratio to 6:1, all based on this so-called „straight run“ fuel. Higher revving engines as well as higher compression ratios had been possible from engineering side of view, but fuel chemistry was the hurdle, as engines started to „knock“ at higher revs. Alternative fuels with higher anti-knock rating had been sought and found, e.g. alcohols (Methanol, Ethanol, Isobutanol, Isopropanol), aromatics (Benzene, Toluene, Xylene), and some other compounds like Acetone, Aniline, etc.
These components had been used to produce racing fuels in the pre-war era, but proved to be unsuitable for standard use due to their aggressive nature, and the low availability. The scientific search for anti-knock compounds finally resulted in lead, in its liquid organo-metallic form Tetra-Ethyl-Lead (TEL), discovered in the early 30s. However, industrial use in large scale only started in the 50s, allowing engineers to construct higher-revving engines, and to increase the compression ratio up to 12:1 – without the feared knock effect. By using TEL the RON could be increased from 70-80 to even 100 plus.

The introduction of the catalytic exhaust converter made the use of TEL impossible, because the lead destroys the catalyst, so alternative octane boosters must be used. Most of them had been known already, like alcohols and aromatics, but commercially available quantities had not been sufficient to retain the high octane ratings achieved from lead. Therefore the unleaded fuel available in the US in the 70s had a much lower RON than the leaded one. The elder of us may remember that the power rating of a standard US V8 dropped from 300 plus HP down below 200, or even 170 HP. The „Clean Air Act“ came too fast, and neither the oil nor the chemical industry was prepared. When unleaded was introduced to Europe in the early 80s, the global supply situation had changed already, so the differential between leaded and unleaded was rather small (91 RON instead of 92 for regular, 95 instead of 98 for premium). The HP figures for cars running on regular remained unchanged, that for engines running on premium gasoline dropped between 0 and 8 % only.

The gasoline sold today is not the same as in the 60s less TEL, it is a complex reformulated compound. Isomerization units convert the straight chain paraffins to iso-paraffins, and reformers the naphthenic hydrocarbons to aromatic ones. Additional octanes are achieved by adding high-octane chemicals like e.g. Toluene, Methanol, Ethanol, MTBE, and ETBE.

Coming to the start of this topic, the agressive nature of unleaded as reported by Yelwoci. Reason for this are not the aromatics as Peter believes, but the Methanol. Aromatics had always been in gasoline, even in the early „straight run“, as they are part of the crude oil. Methanol on the other side is a real „alien“, at appears in Gasoline only by physical blending, and not by nature. Nowadays the Methanol content in gasoline is restricted to 3 %, but in the early days of unleaded in Europe this could be as high as 10 or even 15%! Peter, this is the reason for the „burnt out Sierras“! If you are interested in the physical explanation, send me an e-mail, would be too specific for this topic.

The original sealings, gaskets, fuel hoses, etc. of classic cars are resistant against the gasoline of those days, but mostly not against Methanol. However, this problem should be well known to all manufacturers of such equipment today, so that all new produced spare parts should be Methanol resistant. On the other side, be careful with all original spares you still have in a corner of your garage, or which are found as a „treasure“ at a former dealership. I don’t want to create any panic here, effected are only rubber or similar materials, and sometimes even old compounds are already methanol resistant, but care should be taken.

So what are the conclusions for those of us running classic cars? There are 3 topics, which are
1) the octane rating,
2) the chemical composition of the fuel,
3) the missing lead.

Concerning octane rating I only can talk about the situation here in Europe, have no information about North America and Australia. There is no problem at all with pre-war cars, they all are designed for octanes of less 80, so standard 91 RON regular always sufficient. Any owner of a postwar classic should check his manual for required octane ratings, in some cases 91 regular is okay, other would need 95 Euro. Most high-performance engines will need 98 RON, but in most countries this is available as unleaded also. If not, use 95 and adjust ignition accordingly (3 degrees may be sufficient). The very rare 100 or 102 RON machines must use 98, adjust ignition, and loose a few HPs.

The chemical composition of today’s gasolines is rather „safe“. They contain rather high aromatics percentage, but please do not mix up Benzene and Toluene / Xylene. All 3 are aromatics, but the dangerous stuff is Benzene, which is cancerogene, and banned resp. limited. As long as most standard paint thinners contain Toluene and Xylene, nobody should be afraid for it in gasoline.
The aggressive nature of alcohols, especially Methanol, has been explained already above.
Remaining problem may be the part of oxygenates in gasoline (alcohols and ethers like ETBE and MTBE). As the word says, these are oxygen containing chemical structures, and consequently change the lambda value, as part of the oxygen (air) needed for combustion is already in the fuel.

The „no lead“ topic I believe is point of discussion for years, so I will shorten this item. It is no problem for all pre-war cars, as there was no lead in gasoline in those times (careful with US cars!), and the same is valid for most cars of the 50s. For all others I believe the topic is heated up too much. A friend of mine bought a 1984 Mercedes 500 SEL with 120.000 kms in 1989, equipped it with a catalytic converter, but did not change to hardened valve seats. The car is used in hard daily use since then, has reached now 400.000 kms, and not any single problem with the valves! Okay, this is only an example, and no guarantee of course!

Sorry for this long posting, didn’t expected this when started, but those of you interested may find it useful, the others skipped it anyway.

Phew,

Good post Mr M I have just "wheelbarrowed it but will return when I get more time.

Interestingly Mr Welycoi and myself were at a meeting on Sunday where a gentleman from Millers explained that Super Unleaded goes stale very quickly and its octane rating drops to a lower level that premium unleaded.

Your point about the term "lead free" comes unstuck when converted to French which is of course "sans plomb" 'Without Lead' ;)

Hello Peter,
don’t know the correct wording for „unleaded“ in French, but in German the official wording is „unverbleit“ (meaning unleaded), although everybody calls it „bleifrei“ (lead free). However, as there is no leaded gasoline around anymore, so there is also no risk of contamination nowadays, so unleaded is also lead free,

Sorry, but the Millers sentence I do not fully understand (always consider English not my mother language). What it the difference between super unleaded and premium unleaded?? The ageing stability of a gasoline has nothing to do with the octane rating, it depends on the amount of reactive components (mainly unsaturated hydrocarbons, so-called olefins. When such olefins get partly saturated, they form polymers in form of gums or resins. However, firstly this problem you also have with leaded fuel, and secondly all fuels contain additives to prevent this. Octane rating dropping??? Bu..sh.. (I made the dots by myself)!! The octane number or rating is a physical constant, which cannot change that simple! What was this guy trying to sell you? For sure any expensive additive or something like that! If you let me know some details, maybe I can prepare the right topics for you to catch him!

For somebody really interested in gasoline chemistry & physics, this is a good lecture: http://www.horizon.bc.ca/f1/gastech.htm
Good stuff, although I cannot agree with „Typical mid-1920s gasolines were 40 - 60 Octane”, acc. to my information is was higher.



[This message has been edited by Michael M (edited 22 February 2000).]

Michael,

I'm enjoying this.

We were talking about additives for valve protection and better burning. I can say that the road version of this particular product is currently allowing me to run premium (95 Octane RON) petrol in my MGB without adjustment or hardened valve seats. The performance has improved but we shall see if the additive saves the head. With the additive a litre costs the same as Super Unleaded (98 Octane RON).

What this guy was saying was that the Super unleaded is less stable than ordinary (Premium) unleaded due to the high concentrate of additives which (he says) break down over a short period of time. The UK sales of Super Unleaded are pretty minimal so (he suggests) the petrol gets stale.

He advocates using 95 octane unleaded and his additive rather than 98 Octane plus the additive, The additive is also an octane booster. ;)

This is an important topic so any info you or anybody else can impart will benefit a lot of people.

Mm, I've had a stale petrol problem before now. It seemed to start crystallising in the fuel lines. Most odd.

I'm going for the conversion route myself. I have no faith in my ability to remember to pour the right amount of rocket fuel down the filler every so many tankfuls.

That and the fact that an oil starvation problem has knackered the valve gear on my 1970 Mercedes Benz 220. I'm going to need a recon engine and so I may as well go the whole hog and go for unleaded too.

This is a little off-topic, but the best bet for a Mercedes exchange motor in this country is a pair of firms in Crewe, Cheshire. I don't suppose anyone out there has had dealings with them, and can offer a testimonial, or a beware?

Just a thought.

On the subject of turbos, I saw Practical Classics giving some space to some serious reporting of turbo vane failure in Volvos and Saabs. Seems that this is more than anecdotal now. And the burned Sierra phenomenon is, I understand, alive and well in New Zealand, where the oil companies are under considerable pressure to promote leaded fuel once more, due to the older car population there.

Hello Peter,
okay, Premium is 95 RON, and Super is 98, this I didn’t know. The statement that 98 is less stable than 95 I still consider as bull-etc, at least not within a reasonable period (I’m not talking about 5 or 10 years). Ask some technical people from Shell of BP, I’m sure that they will tell you nothing else. I doubt that their additive is an octane booster, as thousands of researchers in the petroleum and petrochemical industry are looking for this since 20 years, and such formula would be worth billions!
However, there is a difference between an additive and a component. An additive is used in small quantities, normally less than 1 %; a component can form a vital part of the gasoline itself. As an example take lead resp. TEL, it had been added at 0.15 grams per litre, so clearly an additive. Albeit small percentage, it increases RON for about 5-8 points, depending on basis gasoline. On the other side take Toluene or MTBE, both have RON ratings in the range of 118, so for increasing a RON from 95 to 98 you would need about 15 %, so clearly a component, and no additive.
I don’t know what Miller’s stuff is, but most probably none of the common components, as I do not believe one has to add 5 or 10 litres per tank fill.
I also do not understand why RON 95 plus additive should be better than 98 plus additive, except for commercial reasons. The formula is quite simple, a full tank of 95 plus additive costs the same as a full tank of 98, so they have arguments to sell it! For 98 plus additive there are no commercial arguments, so simple it is!

I know that there are some additives around to replace TEL with concerns to valve seats, most of them on basis sodium. I have no idea whether these additives really protect the valve seats or not, but one thing is absolutely clear: they neither increase the octane rating, nor the performance in general. I’m really surprised that your feeling is that the performance of your car has improved, is this really the case, or only wishful thinking? Physically or chemically there is n o t h i n g in a gasoline which improves directly the performance of an engine, except if the basic gasoline is not suitable for the engine in question. If your engine needs 98 RON, and you use 95 only, of course an increase of octane rating to 98 has positive effects. But if you require only 95, then an increase even to 102 RON has no effect at all – except you change the technical specification of the engine, e.g. increasing the compression ratio. In n o c a s e you should use 95 plus any additive, if the engine requires 98 octanes! There is no additive known to me which can increase octane rating, except TEL or other dangerous or even prohibited substances, or of course components like aromatics or oxygenates.

If they offer their product as substitute for TEL with concerns to valve seats – okay, may be it works, but as octane booster?? Would be interesting to know whether they make such statements only orally and personally, or whether they confirm this somewhere in writing in folders or the like.

Hello Tim,
gasoline crystallizing in fuel lines I never heard before, I believe we are not talking about Diesel engine!?

As explained earlier in this topic, ageing gasoline forms some kind of gum or resin, but never in a quantity which effects fuel lines, only injection valves or carburator nozzles, and also normally only if it is really old (1 year plus).

I fully agree, if one needs an engine rebuild anyway, valve seatings should be converted to hardened steel. It‘s only 100-200 GBP more in that case.

Oh, yes, Michael, I had real fun with the gloop I took out of the carb.

The best way I can describe what I found in the fuel lines is a residue of whitish crystal, a little like dried sugar solution at the bottom of a tea cup, only in a very small amount, but guaranteed to go straight into the carburettor jets if it wasn't cleaned out.

On mature reflection, I daresay the crystallising effect could have been some other contaminant. But we are definitely talking aged petrol, as the car in question had been standing unstarted for several years before I got my hands on it.

Typically, though, a flush of the fuel system, a new battery, and the old wagen started on second turn of the key. Mercedes Benz - you've got to love them.

Now that the summer's coming, maybe THIS year I'll find the pressure leak in the power steering system.

[This message has been edited by TimD (edited 23 February 2000).]

The effect Tim describes really looks like polymerization residues, and it is technically logical as the gasoline was some years old. Storing a classical car during winter period does no harm, but after a period of some years one may - not must - expect troubles.

By the way, is it really a pressure leak? I know these old Mercs quite well, and most probably there is only some air in the system. Did you remove the hoses from the pressure pump, e.g. to change engine? Is the system blowing out oil combined with bad working of the power steering? Try it with de-airing (don't know the correct English word) of the system, as it is done with braking systems also. As far I remember (I did this last time as a youngster 20 years ago, no money, but driving Mercedes!) there is a kind of release valve at the steering housing, which has to opened, then turn the steering wheel various times from extreme left to extreme right, simultaneously pour in constantly new oil (ATF, SAE 10). Better use a hose over the valve, as otherwise the oil is spraying all around!


[This message has been edited by Michael M (edited 23 February 2000).]

It's definitely a leak somewhere. Before I took the car off the road, the steering fluid consumption was becoming a major factor in the profit margins of several petro-chemical companies. In driving, the symptoms were a sort of tugging back from the steering, which increased in strength as the lock increased, and which had a rhythm in time with the engine!

Is it any wonder I've taken my car off the road until it's sorted once and for all?

Perhaps I ought to start a Tim's Mercedes Restoration thread. The car has taken five years so far, so if Peter's looking for good mileage in his debates...

Anyway, back to the unleaded petrol issues!

Michael,

Accepting your argument concerning Super unleaded, I know that this will phased out in ythe Uk soon so there's no point in setting a car up to run on it with additives if it ain't gonna be around.

I know from experience that my MGB is running better since using the stuff. Its Millers VSP. The basis of this additive is mangenese. Now I will wait and see if my valve seats degenerate and if so I will build that new engine I've been promising myself.

FYI. My race engine has already beeen converted to unleaded, but I will also use the CVL additive to give extra protection. Its due on the rolling road this weekend ss I can let you know if we get any improvement. Last year we ran on Super unleaded only. ;)

Super unleaded is not being faded out.
I asked BP by email and they intend to keep selling it for ever.

even tho it only forms 3% of sales but they recognise it as a core product

they are aware of this rumour tho, but tis only a rumour.

I was very surprised to learn from Peter that 98 unleaded (Super) will be phased out. Of course it has only small market share all over Europe, but the 98 unleaded was the argument of the oil companies to phase out 98 leaded. There are a lot of older cars around needing 98 octanes - leaded or unleaded -, so phasing out means extreme problems for all owners of cars needing 98. Therefore I believe that THR is right. Don't want to be unpolite, but can it be that such rumour has been initiated by certain companies selling additives??

Well I hope they do keep selling it but my local Fina and Shell garages have stopped it. Maybe I should find a BP garage. ;)

Michael M
Thank you very much for your informed input.
I was relying on my Chemical Engineering knowledge of the 80's and was a little rusty.

Its always a pleasure to find soemone who knows their subject.

I think you asked about the French for unleaded, it is 'Sans Plomb'

The problem with Super Unleaded(98) in UK is that only about 50,000L is sold a month throughout the whole country (&lt;1.5% total sales) and volatiles evapourate changing the mix.

With repect to Millers it is a Manganese base which when used as prescribed gives 80mg/L metal, which enhances the knock value of 95 to about 98. It however is 'advertised' especially to FIA for its valve seat protection.

The EPA in the US are starting to get concerned about Manganese as the believe it contributes to Alzheimer's and Parkinson disease.

IanC

Oilweci,

If you read the other responses I think you'll find that I said that!!!!! ;)

an example

we run a 1600 BDA (for sale)
240 BHP
this runs on all types of petrol

the engine was tuned using super
so this works best
however the quality does vary a lot.
if the fuel is left in 4l cans over a week it deteriotes a lot noticable when warming the engine up, its more fluffy.
fresh feul is best
this also goes for 4* and unleaded tho.

the engine runs on leaded best next.
next best thing, but as this is no longer availble its outta the window.

unleaded is also no good as it doesnt go bang enough!

also we noticed the colour and particually smell of super varies. and affects quality

BP ans Shell still sell super

About Millers manganese stuff: 80 mg/l is 0.08 g/l, last version of leaded had 0.15 g/l, earlier grades 0.4 and even higher. Simple arithmetical calculation, 0.08 g/l manganese = + 3 octane points, so 0.15 = + 6! This is slightly more than 0.15 g/l lead would produce, meaning manganese having better octane response than lead. Sorry guys, but that’s contrary to current state of science!

Only manganese compound known to me producing little octane improvement is
methylcyclopentadienyl manganese tricarbonyl (MMT), which is allowed to be added in quantities of max. 0.008 g Mn / l in most countires. However, it has been reported to increase unburned hydrocarbon emissions and block exhaust catalysts, so it is prohibited e.g. in California. Additionally it is rather expensive, and the equivalent increase of octane figure can be achieved cheaper with components like aromatics and ethers. If even 0.008 g/l has the a.m. negative effects, what about 0.08 then??

What about scavengers? TEL includes ethylene dibromide or dichloride, the hologenates (Br resp. Cl) form halide salts together with the lead, which can be exhausted. Only a small part of the lead is retained in the burning chamber, forming the well-known layer necessary for valve seat protection. If Millers stuff includes no scavengers, the manganese will settle down in the combustion chamber, the longer you use it, the thicker the layer.

As you may know, common alternative to lead as valve seat protector is sodium. Both these metals are rather soft, and exactly this is the reason of their protection property. I’m no metallurgical engineer, but as far I now manganese is a very hard metal, so I cannot see its function.

Phase out of Super 98 unleaded:
Don’t believe majors like Shell will stop it in general, but only for some smaller stations, where they realize turnover is too small.

Yelwoci is right concerning the evaporating volatiles. Part of each gasoline is also a certain amount of C4 hydrocarbons, more common known as butane. This extremely volatile part is needed to create good starting and cold-run properties. As it is a gas, of course part of it evaporates, especially in summer. This has no real influence on the octane rating (butane has approx. 100 RON) and on the ageing process (gum forming), but sometimes when starting and warming-up an engine, as THR found, especially in case of a racing engine.

Of course each gasoline is different from the others. The colour normally has to do with the brand, and the smell with the components. Toluene smells quite different from MTBE e.g.. Also the quality itself differs, e.g. octane rating. The “98” is a required minimum figure, and in case of unleaded oil companies try to stay as low as possible (98.1, 98.2) for economical reasons. High octane ratings for leaded are much cheaper, so leaded 98 sometimes had 99 or even 100 RON. With a normal engine you don’t realize this, but in case of a 240 HP BDA each octane counts.

One can blend his own racing fuel with certain components, but this is illegal for 2 reasons:
(1) Technical rules of FIA and national MSAs are prohibiting this, and
(2) Tax legislation.
Therefore I will not give any details here!

Well I've just got back from rolling road testing my car. I did this to see if there's any difference with running Unleaded and the additive, compared with running Super Unleaded and no additive. Guess what? ;)

Peter, you still owe me the information which octane rating the engine officially needs!

Not sure what you mean by "officially needs" Michael. If you mean what was the engine designed for then I would say 98 octane four star. In fact my engine ran on Super Unleaded last year and as I left you all yesterday with a guessing game I suppose its only fair to tell you that running unleaded and the additive is producing the same power as super unleaded without additive. ;)

Michael.

I was talking about my RACING CAR which is a V6 Capri with 11.5:1 cr. The wholre power curve is exactly the same and all the other statistics (Co etc.) are also identical.

Now. The MGB was running on 4 star leaded until this year. Whilst running on that petrol it would "diesel" (or run on) when switching off. That doesn't happen now. Also the mid range power has increased significantly without any noticable effect on running temperatures and no ignition adjustment.

Your statements assume that a loss of power is acceptable. I am saying that it is unacceptable for a racing car. You must admit that your theory of lower octane only works if you retard the timing to avoid knocking. That in turn ruins performance.

As my engine is a highly tuned racing engine all the arguments about running with lower octane and backing off the ignition are perhaps not appropriate. ;)

Peter, „officially needs“ means that somewhere in your owner’s manual the manufacturer should inform about the required gasoline quality resp. octane rating.
It seems that you did not know this exactly, so it may well be that 95 or even 92 could be sufficient. Again, without this knowledge a rating of the additive is not possible.

Of course the engine is producing the same power, because octane rating has
n o t h i n g to do with power output. As this subject obviously creates misunderstandings, let me explain again.

Example 1:
An engine is designed for a minimum octane rating of 91. If you use regular gasoline, such engine will run without any problems, producing the power output it is designed for. If you now use 95 or even 98 octanes, nothing at all will change. The power output will be exactly the same, because it is based on the mechanical constellation of the engine, and not on the fuel.

Example 2:
You change the mechanical data of this engine, e.g. increase compression ratio by using a thinner cylinder head gasket. Effect of this mechanical adjustment will be higher power output. If you now still use regular (91 RON), the increased power will be recognized, but most probably the engine will „knock“ at certain stages (high revs, accelleration out of low revs). If the increase of compression was only moderately, you can avoid the knocking effect by adjusting the inginition a few degrees earlier, but then of course you will loose again the additional power you achieved before.
If you now change the fuel to 95 or 98 – depending on how much you increased compression - , and adjust the ignition to original data, the power increase is back again, but without the knock problems.

So high octane ratings only i n d i r e c t l y have influence on the power output. Using high octane fuels has no effect at all on the power, you have to change the mechanical specification of an engine to use the advantages of higher octanes. On the other side, if an engine n e e d s high octanes, but is fed with lower octane fuel, there is no reduction in power, and if is driven moderately, even the knock effect does not show off.

If your test with 95 + additive shows no difference to 98 plain, it is obvious for me that the engine needs only 95. In order to answer this question you should do the same test again, this time with 95 plain. The power output will be the same, that’s no question, but interesting would be whether there are some knock effects or not. Important is that such driving test is caried out under comparable conditions. Highly interested to learn the result!



[This message has been edited by Michael M (edited 28 February 2000).]

I researched a little, found out that compression ratio of early 4cyl MG-B was between 8.0:1 and 8.8:1, later models most probably have even less (US legislation). If these figures are correct, I believe 95 RON is sufficient, may be even 91/92 is workable. Peter, if you cannot find this item in your literature, please let me know more details of your car, so that we can try to find out.


[This message has been edited by Michael M (edited 28 February 2000).]

Sorry Peter, I thought you are talking about your MG-B.
Of course loss of power is not acceptable for a racing car, that’s no question.
I stated this clearly in my earlier posting, saying „but in case of a 240 HP BDA each octane counts”.

I also never said that loss of power is acceptable – also not for a road car -, but if the octane rating of available fuel is not sufficient, it’s better to loose some power by retarding the timing than to damage the engine.

“You must admit that your theory of lower octane only works if you retard the timing to avoid knocking. That in turn ruins performance”, that’s exactly what I said, only in other words (“If the increase of compression was only moderately, you can avoid the knocking effect by adjusting the inginition a few degrees earlier, but then of course you will loose again the additional power you achieved before!”).

I know that my English is not the best, but up to now I thought it is at least understandable, sorry if that is not the case.

What is 4 star leaded? Is it 98 octanes resp. the old leaded premium? If yes I cannot understand the diesel effect when switching off. This normally only happens when ignition is adjusted totally incorrect, or if the fuel is extremely low-octane (&lt; 90).

I really don’t doubt your experiences with the MG-B and the Capri, although I do not understand them, as physical rules are put out of force (general rules, not my rules!).

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Michael M:
I also never said that loss of power is acceptable – also not for a road car -, but if the octane rating of available fuel is not sufficient, it’s better to loose some power by retarding the timing than to damage the engine.<HR></BLOCKQUOTE>

Yes whilst you are absolutely right I think the question was originally posed to highlight the problem with the loss of leaded petrol and the lack of performance from unleaded.


<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>
I know that my English is not the best, but up to now I thought it is at least understandable, sorry if that is not the case.<HR></BLOCKQUOTE>

Your English is fine. Don't apologise its superior to my Dutch, German or any other language you care to mention.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>
What is 4 star leaded? Is it 98 octanes resp. the old leaded premium? If yes I cannot understand the diesel effect when switching off. This normally only happens when ignition is adjusted totally incorrect, or if the fuel is extremely low-octane (&lt; 90).<HR></BLOCKQUOTE>

The old four star was supposed to be 98 octane but it was degraded over the years. A modern engine can cope because it automatically changes the timing with every firing of the engine. Old cars don't have this ability.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>
I really don’t doubt your experiences with the MG-B and the Capri, although I do not understand them, as physical rules are put out of force (general rules, not my rules!).<HR></BLOCKQUOTE>

Maybe we're talking chemistry when physics would be more appropriate? ;)

Leaded v/s unleaded:
Here on the continent the withdrawal of leaded was never a problem of octane rating, because besides the Euro Super with 95 RON most stattions also offer the unleaded Super Plus with 98 RON, so no lack of performance at all. I understand that in the UK it's the same, 98 leaded phased out, but super unleaded offered as substitute. So principally only the valve seat problem evident.

Physics v/s chemistry:
Sorry, but octane rating and engine performance is pure physics. May be result of chemistry (blending components, addtives), but nevertheless in it's effect only physics.

BLATANT SPAM!!!! I have an account with Burlen Fuel Systems and can supply stuff at amazing discounts....roll up, roll up get yer SU kit here...also Weber products and Lucas and Bosch K & N and JR and......ouch, whaddya mean your gonna move this post to the classified forum.

Apparantly, the last lot of leaded in the U.K. was sold sometime around October last year- it took quite some time for the oil companies to change the signs etc so we were unknowingly using the cursed L.R.P.(spit!!) for a few weeks, which could go some way to explaning the sudden onset of knocking and loss of power in our Granada, not to mention the carb problem!
We are now using unleaded with a potasium based additive in all our cars (1984 2.3 Granada, Vincent Hurricane with a 1500 Spitfire engine and a Dutton with a 1300 Xflow) They all seem to be quite happy with the stuff.
I heard a rumour that a small oil company has been granted a licence to sell leaded 4-star in the U.K. anyone know anything about this?

There is a list on approved petrol stations that can sell 4*
dont have it tho!

theres a petrol station in Great Torrington that sells it tho.

That's what I'm saying. However I have hardened seats in my engine so I could run S/ul. I am somewhat sceptical about the "stale" S/ul issue but having had the seed planted I am also worried that I may blow up what is an extremelty expensive component.

Phew !!! what a posting this has turned out to be, think I need a rest after reading all that.
Anyway for the UK based racers... according to the MSA leaded fuel (4*) can still be sold in the UK if you have the appropriate license. They say that all circuits that have pumps will sell leaded 4* fuel this season - but at what price I wonder ?
Last year I ran my Kent FF1600 on a 50/50 mix leaded to super unleaded. This year I was thinking of using 100% super UL but from what your saying Peter I may be better off with Premium plus the Millers VSL ?

Hi Micheal,
Lots of companies sell octane booster,one even calls its product Octane Booster.I believe these products are usually Toluene or Acetone based.why do people not use industrial methanol as fuel it is really cheap or do you get told off for not paying the road duty.Or is there another reason.
graham

Graham, good question.
The only pro of MeOH is its high octane rating, but there are lot of contras.
The calorific value of MeOH is about half that of gasoline (or petrol, as you say in the UK), that means for same production of energy double quantity is needed. As you can see from my profile, I’m trader in chemicals, and I traded MeOh and also Gasoline for more than 20 years now. MeOH was always cheaper than gasoline, but never – except today – below 50 % gasoline. Another hurdle is the mineral oil tax which is due on volume (at least in most European countries), so it also has to be doubled. Use of MeOH (and other chemicals like Toluene, MTBE, etc) without paying the corresponding tax is illegal. In chemical business you have to prove the final destination of any tank truck of „fuel substituting chemicals“, and these files are controlled by authorities. There are also a couple of technical problems. MeOH is poisonous, and it is hygroscopic (collects water from the air). Main problem is the fact that it is a pure chemical, meaning it has a fixed boiling point (abt. 80°C). Gasoline is a hydrocarbon mixture, with no boiling point but a boiling range which starts at abt. 30°C and goes as high as 215°C. Advantage is that the fuel is carburated constantly at all temperatures, it has good cold-starting properties, but also works properly in extreme heat.
As you may know motor industry is working on MeOH as fuel since years already, but instead of combustion engines running on MeOH latest developments go more into direction fuel cell (MeOH to Hydrogen).