Questions about WWII 87 octane aviation fuels

Hello everyone,I have some question about the aviation fuel in BOB:

1. Is the British "87 octane fuel" really 80/87 octane?

2. Which fuel is better, German 87 octane fuel "B4" or the " British 87 " ?

Thanks much for any help you can provide.

Fighter Command of the RAF used 100 octane fuel during the BOB, the rest of the RAF used 87 Octane.

87 octane fuel is 87 octane fuel, but there are multiple methods of measuring octane rating. Its important to use the same rating when making a comparison.

For German aviation fuel ratings, see these papers:

Kurfrst - TECHNICAL REPORT NO. 145-45 MANUFACTURE OF AVIATION GASOLINE IN GERMANY.
http://kurfurst.org/Engine/Fuel/Rep...ion_gasoline_via_Fischer-Tropsch_Archives.pdf
http://kurfurst.org/Engine/Fuel/mof...ng_Products_via_Fischer-Tropsch_Archieves.pdf

As for the use of 100 octane fuel in the BoB, Glider, lots of claims were made, little evidence has been seen what fuel Fighter Command was running on, and to what extent.
I guess currently its more of a question of faith, than a matter of verifiable facts.

Kurfürst said:

I guess currently its more of a question of faith, than a matter of verifiable facts. Its certainly a dear enough subject for some to bother with creating new logins from time to time.

Click to expand...

Two points
1) I do hope that you are not accusing me of having multiple logins, if you are you can withdraw it.
2) I totally agree about your case being a matter of faith over substance

1, No, not at all. I think you are an honest and great guy to discuss and even to disagree.
2, Yup.

TKS for Kurfürst,but my questions are:

1.German 87 octane fuel "B4",in CFR Motor is octane 89-91,but in"rich mixture",the number is only 81; at what the C.F.R. Motor number reading of the British 87 octane using at the rest of 1940?

2.I think that the "avgas 87" in now days, 80/87 octane, has many different from Germany "B4".for example，color and grams leading. What about the " British 87 "and german B4 ?

3. In some altitude, DB601A using B4 fuel has the better power than +6LB MERLIN ,Which fuel is better, German 87 octane fuel "B4" or the " British 87 " ?

Due to different manufacture techniques and additives between nations, German and Allied aviation fuels are not very compatable when comparing burn qualities and knock ratings, where British and American fuels may have tended to seek more commonality.

The rough measures between them are for the PUMP octane rating:

B4 "new standard" aviation fuel for fighters is 90 octane
C3 "high performance" aviation fuel is 100 octane
British "standard aviation grade" fuel is 85 octane
British "high performance" 130 grade aviation fuel is 115 octane
American 150 grade is 125 octane

But these figures cannot reflect overall performance, the traditional notation is:

B4 average motor method 87.5/91RON
C3 motor method 94/104RON
British 80/87 it explains itself
British-American 100/130 again self explanatory
American 100/150 we're just repeating ourselves now

And according to these figures when an engine is under loading (for example in the climbing condition)...

British 80/87 is a good 7-8 points down from
German B4 which is a good 6-7 points down from
German C3 which is 6 points down from
130 OR 150 grade.

However such things as octane ratings using whatever method do not adequately reflect the burning qualities and knock rating under specific conditions. The type of supercharger and engine layout will affect a fuel's knock rating. The method it was manufactured and its composition will affect the research rating. Combine them for a pump rating and what you get is not really more authoritive than a commercial television advertisement.
"By BP fuel, it's got 464000 little octanes just waiting to drive your car for you." But it detonates at 35 degrees when exposed to aluminium.

*shrug*


[credits to Kurfürst for a magnificent database to really narrow down looking up these things, cheers mate]

And how mutch difference in poweroutput does it give out betweens those types of fuel?

I feel a bit weird just sort of floating in to the site without really being around lately long enough to get to know the regulars...and I don't want to go snipping anyone's nosehairs by acting like the answer-man. So let's take everything I say here as opinionation and perfectly open to correction.

I've done a little race engine building and used computer modelling (with good engineering software like Engine Analyzer Pro) to help cut expenses in trial and error for parts sizing, component matching, desired valve timing and ignition curves under varying operating conditions and application requirements.

If we use a general fuel manufacture called "fuel A" and give it various pump rated octane forms like "fuel A1, fuel A2" and so on, then you could look at the differences like this:
higher octane burns at a higher temperature and is less explosive so it loses power, but these factors allow an increase in dynamic compression and spark advance so you get a net increase in output so long as you perform these modifications in a motor supplied with higher octane fuel. This is especially easy for supercharged engines as it simply means higher octane, lower torque production at the same boost, more boost, more net output than the old boost/lower octane.
So octane needs to be suitable for the engine type and its mechanical layout.


That being said octane rating isn't the only quality which relates to the flame performance of fuels. British and American 100/130 grade equivalents were different (the American one was called Ammendment 5 with a big serial number, we got it here in Australia and the RAAF ran up to +20lbs on F3R and F4R Allison motors with it, but it is considered roughly equivalent to the British fuel that topped out at +12lbs in a Merlin without intercooling).
Using American 100/150 grade intercooled Merlins were pumping up to +25lbs pressure into the manifold.
In 1944 the Germans were pumping +12lbs without intercooling or charge coolant of any sort (ie. no MW50) on C3 fuel or a little over +14lbs using MW50, but they ran much higher compressions (something like 8.4:1) so it is also a very good reflection on knock index, whilst similar power outputs puts it en par with the Allied fuels at the time for burn qualities.

Your lower grade fuels of course limit power production without extensive engine development to overcome its hurdles, but improved cylinder head design, flow dynamics, cooling and ignition can help immensely. The Soviets were infamous for poor qualities fuels but managed 1650-1800hp out of their late war fighter engines, one being based on the Hispano-Suiza and the other can trace its roots to American radials back in the mid thirties.


It's a complicated question, and probably requires more engineering knowledge than I have to explain succinctly.

but it is considered roughly equivalent to the British fuel that topped out at +12lbs in a Merlin without intercooling

Click to expand...

Spitfire Vs were run at up to 18 lbs without intercoolers.

As for the use of 100 octane fuel in the BoB, Glider, lots of claims were made, little evidence has been seen what fuel Fighter Command was running on, and to what extent.
I guess currently its more of a question of faith, than a matter of verifiable facts.

Click to expand...

It certainly is.

We have the consumption figures from the national archives,

June - August 1940
10,000 tons 100 octane a month
26,000 tons other grades a month

September
14,000 tons 100 octane
23,000 tons other grades

October
17,000 tons 100 octane
18,000 tons other grades

We know that even 10,000 tons a month is far more than Fighter Command needs. We know that we have combat reports from almost every Spitfire squadron mentioning the use of 100 octane.

Then we have a posting by an Australian called "Pips" who gave a précis of what he remembered seeing in the Australian archives that contradicts everything that's actually been published from the UK archives.

It certainly is a matter of faith. Documentary evidence against the opinion of an anonymous poster. What other reason is there to favour the opinion of the anonymous poster?

Of relevance here, is an extract from Wings of War - edited by Laddie Lucas p.57; which refers to No 263 Squadron, led by Squadron Leader J W Donaldson ('baldy' to the Service) - after leaving HMS Glorious 150 miles off Norway in 1940.
"Having got down on Lake Lesjaskog, the squadron found there were no refuelling tankers, only 4-gallon fuel cans and there were full of 100 instead of 87 octane spirit. This meant that the engines would overheat and in due course seize up"
Significant - in that if Britain was so short of 100 Octane, why is it going to Norwary in April!? Seems, if it was available then to be loaded on ships in Scotland, it would be available a few months later for Spitfires Hurricanes.

Hop said:

Spitfire Vs were run at up to 18 lbs without intercoolers.

Click to expand...

Cheers thanks. I thought the 40-50 series had +12lbs max same as the 20 series. Do you have the guidelines for this setting?
It actually helps me with another argument about F3R/F4R motors being run at 66" and 70" MAP in the field on "100 octane" fuel. One detractor claims if the Merlin can't do it in 1942, the Allison can't. Well this statement says the Merlin was doing 66"Hg just fine in 1942.

If you go over to Mike William's Spitfire site you can see the test of AA 878. Spitfire V, Merlin 45: Spitfire Mk V AA.878 Report

The test says 3 minutes at 16 lbs, 3000 rpm, but the Spitfire V manual I have says 5 minutes.

18 lbs was only for the "M" engines, according to the manual.

16 lbs seems to have been authorised by August, as instructions for fighting the Fw 190 dated August 1942 say 16 lbs "has now been authorised".

Mike also has a page on W 3228, Spitfire Vb with a Merlin 50M, showing the use of 18 lbs. That's dated May 1943, but I'm not sure when they started 18 lbs in service.

Spitfire Mk II pilots notes, published July 1940 states that it uses 100 octane fuel, absolutely no mention of 87 octane.

There is also evidence that Bomber Command was cleared for 100 octane in 1940, seems odd that the RAF would use 100 octane in bombers while their fighters were sputtering around with 87 octane.

claidemore said:

Spitfire Mk II pilots notes, published July 1940 states that it uses 100 octane fuel, absolutely no mention of 87 octane.

Click to expand...

The copy I got of Spitfire Mk II pilots notes, published July 1940 definietely does mention seperate limitations for when 87 octane is used:

Hop said:

We have the consumption figures from the national archives,

June - August 1940
10,000 tons 100 octane a month
26,000 tons other grades a month

September
14,000 tons 100 octane
23,000 tons other grades

October
17,000 tons 100 octane
18,000 tons other grades

Click to expand...

Great, do you have a reference to that particular paper?

Hop said:

We know that even 10,000 tons a month is far more than Fighter Command needs.

Click to expand...

Actually, we only have the word of an anonymous Brit (you) for this, but no evidence.

We do know however that when the RAF considered to supply of 150 grade fuel in November 1944 for some 35 Spitfire Squadrons in the 2nd TAF, they reckoned that some 15 000 tons of avgas will be required per month.

Fighter Command in 1940 had some 50 to 60 Fighter Squadrons, however, and yet you say that they were able to run twice the number of Fighter Squadrons on less fuel...?

Hop said:

We know that we have combat reports from almost every Spitfire squadron mentioning the use of 100 octane.

Click to expand...

Indeed. You only forgot to mention that, for some odd reason, there is never more than about four or five Squadrons (out of about sixteen) mentioning the use of 100 octane fuel in the same month.

Thing is, the Squadrons only seem to report using the emergency boost (that was only available when 100 octane was available) when they are stationed at some specific fighter stations; when they were redeployed (and this happened a lot during the Battle), suddenly they do not report it any longer.

It is because some Stations - and not Squadrons - were supplied with 100 octane fuel (which is BTW proven by National Archive documents), and others were not. Currently there is indirect evidence (combat reports) for maybe half a dozen fighter Stations being supplied with 100 octane fuel, but there were about 50 active stations during the Battle.

What you are telling us, is that because there were about 5-6 Stations supplied with 100 octane fuel, all the other were, too. There is very little about the Hurricane Squadrons, which were the majority of the force, but for some reason, you assume that those must have been supplied, too.

There's no evidence involved in that, only faith that they were.

Then we have a posting by an Australian called "Pips" who gave a précis of what he remembered seeing in the Australian archives

Click to expand...

Nope, we have the notes of an Australian, who BTW gave the title of the paper, and where it could be found for anyone else to check, and of course we have an Englishman called "Hop", who wants to distort the story about it bit.

....that contradicts everything that's actually been published from the UK archives.

Click to expand...

Nope, that is something you keep repeating because you don't like the contents of what was found there and you want to dismiss it; and you keep repeating it despite being proven false on this claim dozens of time already. You simply want to mislead others.

For example, one the claim you make to dismiss it is that Pips notes that the use 100 octane initially allowed for +9 lbs boost; you always keep telling people that was false and a 'mistake', because the boost allowed was +12 lbs, and for this reason, the whole paper is 'unreliable'.

You never offer any no evidence to this of course, but then again, you were already shown several times the ratings for Merlin III engines as of March 1940, which indeed show that initially +9 was the limitation for Combat purposes. Anybody can check this is true, you only tried that trick a couple of months ago, on this board.

Actually Pips findings are in pretty good agreement with the stuff found so far in the National Archives.

It certainly is a matter of faith. Documentary evidence against the opinion of an anonymous poster. What other reason is there to favour the opinion of the anonymous poster?

Click to expand...

Well, I do agree that there is very little to support to opinion of the anonymous poster, ie. you. That's why I said already its more of a matter of faith, until some hard evidence can be produced with the number of Squadrons involved.

Until then, its mere faith and guesswork.

BTW an interesting paper that Glider posted in some of older threads:

Kurfurst
Please don't quote just the one paper that was posted on the earlier thread without the rest. It is totally misleading and I formally object to you putting it in out of context.

As for your comment about the Australian paper
Nope, we have the notes of an Australian, who BTW gave the title of the paper, and where it could be found for anyone else to check,

I lost track of the times you have been asked to supply a copy of the paper. You know that I approached the Australian archives where I was assured by you where it was held and I sent you their reply, they had never heard of it and could not find it.

The only thing that we agreed was that it up to the person making the claim to support their claims with evidence and you had not supplied this paper or anything else to support your comments.
This paper you keep on mentioning is to support your view, so supply a copy.

For those who have not seen the previous thread this is a link

http://www.ww2aircraft.net/forum/technical/use-100-octane-fuel-raf-during-bob-16305.html

Hi Kurfurst. Read point 8 in that report.
Do you honestly believe that in light of the imminent invasion of Britain by Germany that they would still be flying only 16 squadrons with 100 octane nearly a year after those notes were made?

The onus here is not on Hop or anyone else to prove that 100 octane was in general use, the onus is on the revisionists to prove that it was not.
It has been accepted for almost 70 years that 100 octane tipped the scales during the Battle. If anyone believes otherwise, then they must offer conclusive proof.
I'd love to see even some anecdotal evidence showing complaints from RAF pilots that they had only 87 octane on certain days or when flying from certain stations and that they were unable to catch 109s because of it.

From the Mk II pilots notes (Air Publication 1555B) concerning fuel and oil to be used:

Glider said:

Kurfurst
Please don't quote just the one paper that was posted on the earlier thread without the rest. It is totally misleading and I formally object to you putting it in out of context.

Click to expand...

You didn't support anything else than this, so please stop claiming there was 'context' - unless that 'context' is that you claimed that it - that there were only sixteen plus two squadrons - was 'revised' later, but when asked about when, and to what extent was it revised, and wheter you can supply a copy of that alleged 'revisement', you went dead silent.

As for your comment about the Australian paper
Nope, we have the notes of an Australian, who BTW gave the title of the paper, and where it could be found for anyone else to check,

Glider said:

I lost track of the times you have been asked to supply a copy of the paper.

Click to expand...

I have lost track of the times you were told the reference to the paper, the thread, and who was that it originally supplied it, so why don't you just stop to pretend not getting the fact that it was found by somebody else?

Glider said:

You know that I approached the Australian archives where I was assured by you where it was held and I sent you their reply, they had never heard of it and could not find it.

Click to expand...

IIRC actually you said they told you that they need a precise reference to find it, and ever since it appears you came up with a whole different story about never having heard of it etc.

Glider said:

The only thing that we agreed was that it up to the person making the claim to support their claims with evidence and you had not supplied this paper or anything else to support your comments.

Click to expand...

Please stop lying.

The only person who has to support his claims is the one who has made positive claims, and that being you, claiming that each and every fighter squadron of Fighter Command was running on 100 octane fuel, and for which you so far failed to support any documentation.

My position is that given the several papers pointing out the contrary - the Spitfire II notes, the findings in the Australian Archieves, in the National Archieves, and most ironically, the paper mentioning 16+2 Squadrons (out of ca60) you supplied and now object to be posted - makes it quite clear that it was much more limited than what some here, including you, are wishful for; and that the evidence is certainly lacking to make such positive statements, with which - do I need to brush your memory a bit - even you did agree on this very thread...

This paper you keep on mentioning is to support your view, so supply a copy.

Click to expand...

Well, it is you who claim all fighter squadrons were operating on 100 octane fuel, so kindly support it with the same evidence you ask for, and stop that odd and silly attitude that it is others who have to prove your claims wrong, otherwise its correct.

I can supply you the findings of Pips, however, as much as you hate them:

Pips said:

The first bulk shipment of 100 octane fuel had arrived in Britain in June 1939 from the Esso refinery in Aruba. This and subsequent tanker shipments from Aruba, Curacao and the USA were stockpiled while the RAF continued to operate on 87 octane petrol. Having secured what were considered reasonably sufficient quantities of 100 octane, Fighter Command began converting its engines to this standard in March 1940, allowing boost (manifold) pressures to be raised without the risk of detonation in the cylinders. This initial increase in maximum boost from 6 lb to 9 lb delivered a useful power growth of around 130hp at the rated altitude.

By the time of the invasion of the Low Countries by Germany in May 1940 the RAF had converted approximately 25 % of it's total fighter force to 100 octane fuel use. The subsequent escalation in air activity and demands placed upon Fighter Command over the next two months put great strain on both the 100 octane fuel stockpiles and aircraft modified to use the fuel. Against the backdrop of total war the RAF found that it's reserves of 100 octane fuel was well below the level considered necessary for widespread use, for any sustained length of time.

Two actions were immediately undertaken by the British War Cabinet in May to resolve the looming crisis. Firstly 87 octane fuel was deemed the primary fuel source to be used until further supplies could be discovered and delivered in sufficient quantities to allow the Merlin conversions to again take place. Those existing fighters already so converted (approximately 125) would continue to use what supplies of 100 octane were available, but all other fighters that had not been modified to continue with the use of 87 octane (of which there was more than adequate supply). The second action was for the British Government to contract the Shell Oil Refining Company to assist the British-controlled Iraqi Petroleum Company at Kirkuk to produce 100 octane fuel. This arrangement proved quite successful as production was quickly converted to 100 octane fuel.

The first Middle East shipment of 100 octane fuel arrived in Portsmouth on 12th August, with a further two deliveries in September and four in October. Although too late to allow widespread conversion for the use of the fuel the deliveries did ensure that from this point on Britain would not be lacking in 100 octane fuel levels. With the newfound supply RAF Fighter Command again embarked upon a Merlin II and III conversion to 100 octane use from late September, finally achieving 100% conversion of it's fighter force by the end of November in 1940.


I came across it when I was in fact researching another subject (Dutch East Indies Fuel levels prior to the Japanese Invasion) at the Australian War Memorial Archives.

It's from a document, copied to the Australian Military Commission in England in February 1941, by Roll Royce to Lord Beaverbrook outlining past, current and proposed changes to the Merlin; and factors that affect it's performance.

It was quite an interesting paper actually, even though i found it to be a very dry subject.

It was a collection of lose-leaf typed pages, included as an addendum in a report titled Fuel Supplies to The British Empire And It's Commonwealth; Outlook, Ramifications and Projections For The Prosecution Of The War.

The reason why it is included amongst AWM papers is because the Australian Government at that time was protesting vigoriously about the continued supply of lower grade 87 octane fuel when it too wanted 100 octane for the RAAF.

I believe that McFarland, Pugh, Hart, Perret, Lumsden and even Churchill have all quoted parts from the report.

Click to expand...