Use of 100 Octane Fuel in the RAF during BOB (2 Viewers)

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Glider

Captain
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Apr 23, 2005
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All
I promised to do some digging and come up with a summary of what I found on this topic which is the following. First of all I must thank a number of you for helping me track down the relevant documentation, there are too many to name but you know who you are and the assistance is much appreciated.

I will do this in two stages:-
a) First of all a 'dry' account based on the original documentation with a comparison of this compared to the view as laid out by Kurfurst
b) Various other sources that support the position as put forward in the original documentation.

In addition I will try to keep the timeline clear.

16th March 1939 Meeting held to consider the question when 100 Octane Fuel should be brought into use in the RAF and the number and type of squadrons involved.

There are three main parts to this.
i) It is true that at this meeting authorisation was given for 16 fighter squadrons and two twin engined bomber squadrons be converted to be use 100 Octane fuel by September 1940. The change over to start at the end of 1939 and the ACAS would select the squadrons.
ii) It was anticipated that these units would use 10,000 tons of fuel over a twelve month period and this would slow down the aim of achieving an 800,000 ton reserve.
iii) The AMPD asked that he should be kept informed as to the progress of the production of the 100 Octane fuel in order that the change over of squadrons could be kept under review in the light of any acceleration or diminution in Supplies.

Compared to the position held by Kurfurst
A number of differences are apparent.
- Clearly this is a peace time plan, the war hadn't started, 18 squadrons would use a lot more than 10,000 tons over twelve months when at war. It is certain that when war started there would be changes.
- It covers both fighters and bombers
- They were not defined as being Blenheim just twin engined bombers of which the RAF had a number of types.
- The 18 squadrons wasn't a fixed number, it was open to change.
- To the best of my knowledge the 18 squadrons in question were never identified. This is not a surprise, as you would only nominate the units when you start preparing to use the fuel, to allow for training and other preparatory work.

14th November 1939 letter re the tests of 100 Octane in the Hurricane and Merlin
In this letter it mentions:-
i) That the tests were successful
ii) The policy of immediately going over to the use of 12 lbs boost is being strongly urged by Fighter Command
iii) The decision is dependent on the availability of sufficient stocks of 100 Octane but that it is understood that there are adequate reserves for this eventuality

7th December 1939 Letter from FC Admin to HQ
This letter starts going into the nuts and bolts of how the change from 87 to 100 Octane would need to be handled. It's the sort of information any change of this magnitude will need.
The most interesting part is that it lists the operational stations at which the fuel will be required in the first instance.

Difference to Kurfurst Position
- Kurfurst still believes that the reference to relevant stations means only those that were hosts to the 18 squadrons mentioned in March but never identified, when the list contains 21 stations all of which are likely to have more than one squadron.

12th December 1939 Letter from Director Of Equipment re Issue of 100 Octane FuelLetter confirms that 100 Octane Fuel is approved for use in Spitfire, Hurricane and Defiant aircraft. Issue to be made as soon as the fuel is available at the distribution depots servicing the fighter stations concerned. Some bomber units may be given priority.
The date of use is dependent on when the fuel can be put down in bulk at the distribution sites and the relevant stations. Re the latter as a station empties a tank of 87 Octane it will be replaced with 100 Octane.
Observations
Clearly this is a change to the March notes. Certain aircraft are included and other aircraft in Fighter Command are excluded, no Blenheim fighter units are included or are any Gladiator units.
There is no limit set to the number of squadrons or area such as 11 Group, or any reference to specific squadrons. The RAF decided to use the 100 Octane and instead of limiting it to a number of squadrons, have decided to limit it by type of aircraft.
In my opinion, the statement of relevant stations can only mean those with Hurricanes, Spitfires or Defiants as defined as needing the fuel in the first instance.
It's fair to mention that Gavin Bailey says that the authorisation came in February 1940. I suspect he may have been in error as the source is the original letter confirming a decision that had been made. It could be that original authorisation referred to in this letter might have had some conditions applied referring to February, I simply don't know.

Difference to Kurfurst Position
- Kurfurst believes that the reference to relevant stations means only those that were hosts to the 18 squadrons mentioned in March but never identified.
 
18th May 1940 Summary of Conclusions of the meeting of the Oil Co ordination Committee
The key points here are:-
i) The Committee took note that the position of the use of this fuel in Hurricane and Spitfire aircraft had been made clear to Fighter Command.
ii) Satisfaction was expressed that the units concerned had been stocked with the 100 Octane Fuel
iii) The Minutes were to reflect the appreciation of the work of the Petroleum Board and that the Air Ministry had been impressed with the manner in which the work had been executed.

Difference to Kurfurst Position
- Kurfurst believes that the reference to relevant stations means only those that were hosts to the 18 squadrons mentioned in March but never identified.

Reference to Gavin Bailey
Whatever the possible cause of confusion re the timing of the Authorisation (see 12 December), there is agreement that use of the fuel began in fighter command from the 18th May. after the stations selected had received their stocks of the 100 Octane fuel.

1st August 1940 Memo from Downing re the Handling of the Merlin EngineThis note is advising the pilots that there is an increase in engine failures in the overuse of the emergency 12lb boost.
The interesting thing is that this memo was sent to ALL fighter groups. Had we been talking about the 16 squadrons or less this would not have been the case. It would have been sent to the squadrons involved.

7th August 1940 Note confirming that the Use of 100 Octane had been authorised for all Commands.
This speaks for itself.

Consumption InformationThe following information are the consumption details of fuel during the BOB period. This information has come from the War Cabinet Oil Position Monthly report that is available from the National Archives.

Consumption of Aviation Spirit
The following figures are for the whole of the RAF and are the Average Monthly Consumption

September – November 1939 16,000 tons
Dec 1939 – February 1940 14,000 tons
March 1940 – May 1940 23,000 tons
June 1940 – August 1940 10,000 tons (100 Oct) 26,000 tons (87 Oct)
Sept 1940 – November 1940 15,000 tons (100 Oct) 18,000 tons (87 Oct)

Point of Interest
The total Usage of the RAF fuel for June – August 1940 period and Sept – Nov 1940 period is essentially unchanged allowing for the reduction in daylight fighting and the reduction of the raids on the Barges by night. However there is a clear increase in the use of 100 Octane that can only come from the release of the fuel for other commands.

Reserves Information
The following information are the reserve stocks of 100 Octane fuel during the BOB period
This information has come from the War Cabinet Oil Position Monthly report (a) that is available from the National Archives, as well as Gavin Baileys paper(b) and Wood and Dempster(c).

Stocks of 100 Octane
30th September 1939 153,000 tons(b)
27th February 1940 220,000 tons(b)
31st May 1940 294,000 tons(a)
11th July 1940 343,000 tons(b)
31st August 1940 404,000 tons(a)
10th October 1940 424,000 tons(c)
30th November 1940 440,000 tons(a)

Point of interest. From the start of the war until the end of the BOB the reserves never dropped and continued to increase. There was never any danger of the supply of the oil running out.

In this summary I have not touched on the other papers, sources links that exist and support the view that Fighter Command was effectively fully converted to 100 Octane by May 1940. They were posted on the Me110 Hurricane Thread and we know they exist.
 
an article by Bill Gunston
"One vital factor often overlooked in accounts of the BoB was the power increase RAF aircraft obtained from using 100 octane fuel. To get an octane rating of 100 required a very complicated process which done on a commercial scale required a large and exspensive refinery plant. Though Dr. SF Birch of Anglo -Iranian's laboratory at Sunbury on Thames was the pioneer of this alkylation process it was the US Army Air Corp that pioneered 100 octane aviation fuel . Probably nothing would have happened in Britain had it not been for a great engine man Air Commodore Rod Banks who Jan 1937 urged that RAF engines should be able to use 100 octane " even if the supply of such fuel were limited, because the use of high -duty equipment might prove decisive in the air in the early stages of a war"
Accordingly , two British emgines one of them the Merlin ,were tested and developed to run on 100 octane which was available only from abroad . Eventually an outstanding fuel called BAM 100 ( British Air Ministry 100) was developed , and the first cargo was shipped to Britain from the ESSO refinery in Aruba in June 1939. The Air Ministry stockpile the valuable fuel which was dyed a distinctive green the fact remained unknown to german intelligence. This stockpiling went on throughout the war , but in may 1940 when the chips were down and everything counted the RAF began to use the special fuel in the Merlins of Fighter Command"
 
I guess the 64k question is, did the RAF enjoy an advantage in its fuel over that of the germans in 1940. I used to think that it did, then the German supporters of this forum pointed out that the Germans developed fuels of similar octane rating, but later still I came to believe that this higher rated German fuel did not begin to be delivered until 1942, or thereabouts.....
 
I don't think that there is any doubt that the RAF enjoyed a significant improvement in the performance of its aircraft by using the 100 Octane Fuel. Germany did have 100 Octane but it seems to be very limited in its availability. Its worth remembering that the DB605 was designed for lower rated fuel. I have little doubt that Germany would have given its eye teeth for the sort of reserves that the UK were able to build up.

The Merlin went from around 1000hp to 1300hp with the new fuel and the increase in boost. Add that to the introduction of the CS Propeller at the same time and you have a serious improvement.

Kurfurst did point out that some of the 110's in the BOB had 100 Octane but I don't know what sort of improvement it gave performance wise. Some 109's also had it but it seems to have been a very small minority.
 
As the author of the EHR article in question, I would like to clarify two points.

1. The March 1939 decision over the use of 100-octane fuel was a pre-war plan which simply indicates that the RAF had begun stockpiling and planning the use of 100-octane fuel before the crisis of 1940 and that the received wisdom of Standard Oil BAM-100 shipments from Aruba arriving 'just in time' (as demonstrated by the Gunston quote reproduced in the thread), is not historically correct.

2. That March 1939 decision was over-ridden by a series of subsequent planning decisions, including critical ones made between February and May 1940 (which are cited in the original article) to begin and expand the immediate operational use of the fuel.

Both of these points should be clear to anybody reading the original note in EHR; and nothing in my work either can or should be used by people attempting to argue that 100-octane fuel was not in widespread use in Fighter Command during the Battle of Britain. That position is contradicted by a mass of original evidence cited in my work (and elsewhere). The next time anyody attempts to produce carefully-selected references from my work to contradict the historical use of 100-octane fuel by the RAF in the Battle of Britain, please refer them back to my original article which if nothing else should provide them with sufficient primary source evidence to disabuse them of that notion.
 
Mr. Bailey,

First, thank you for posting in this discussion. Do you have perhaps any information as to how 'widespread' the use of 100 octane fuel was in Fighter Command from May 1940, how many Squadrons were using it etc?

Certainly there are some extremist opinions that which suggest that each and every Spitfire and Hurricane was running on that fuel, at all time. So far however, no evidence at all was produced that would support that point of view and without the evidence, the statement would appear to me as mere wishful thinking.

In particular, it seems that there is evidence in May 1940 decision was made to stop existing conversion on the basis of the uncertainity of the supplies, and that around 1/4 of the Squadrons were supplied with this kind of fuel during most of the Battle.
 
Aviation fan like I am can be easily digging up the mere figures but learning about the fuels and aircraft performances on this thread is quite enjoyable. In the case of Japanese aviation right before WW2 was that we were certain about how the 100 octane avgas meant. Moral Embargo inhibited us to build refinery plants for it but on an experiment a Mitsubishi Kinsei engine originally rated at 1000hp on 91 octane had performed 1400hp on special high octane AVGAS imported from the US. The IJN produced and used 91 octane gasoline for the fighters and the bombers during the war. In this the Nakajima Homare or Ha-45 engine which aimed at performing on 2000hp class was designed with an assumption of using the 100 octane aviation gasoline. But it was not in the case as it is well known.
 
Mr. Bailey,

First, thank you for posting in this discussion. Do you have perhaps any information as to how 'widespread' the use of 100 octane fuel was in Fighter Command from May 1940, how many Squadrons were using it etc?

Certainly there are some extremist opinions that which suggest that each and every Spitfire and Hurricane was running on that fuel, at all time. So far however, no evidence at all was produced that would support that point of view and without the evidence, the statement would appear to me as mere wishful thinking.

In particular, it seems that there is evidence in May 1940 decision was made to stop existing conversion on the basis of the uncertainity of the supplies, and that around 1/4 of the Squadrons were supplied with this kind of fuel during most of the Battle.

Kurfurst
When if ever are you going to supply any evidence to support your statements!!
All the statements in my summary are supported by original documentation including the statements on the level of supplies. This you have seen on the thread of 110 vs Hurricane. If original documentation is not good enough for you can I ask what is good enough.
I should point out that your only 'evidence' is a paper that you cannot produce, cannot supply a link to and one that the supposed holders of such The Australian War Records Office have not been able to find or even have heard about.
This stacked against a raft of original documents showing a natural progression in such a decision process doesn't amount to a tin of beans. But despite this obvious blinding anomaly, the original documentation isn't good enough for you but your mystery paper is.

However back to facts, the papers showed a monthly usage of 10,000 tons of 100 Octane a month, against a stockpile of 294,000 tons as at the 31st May, almost a two and a half year stockpile. Where exactly is the shortage you keep going on about?
After all it is this shortage, which forms that basis for your evidence of a decision to stop the roll out of 100 Octane. So all we are asking you to do is to provide some evidence to support your theory.
 
For a start you need to research the decisions made on the 7th, 8th and 9th Meetings of the Air Ministry's Oil Co-ordinating Policy Committee on 18th May, 29th June and 10th August 1940, respectively. These can be found in AVIA 10/282 at the Public Records Office, Kew. I believe this source is cited in my original article, which you should not selectively quote to support a thesis which it explictly contradicts.

Now in return I'd like to know what evidence you have which demonstrates that operational squadrons in Fighter Command (and particularly 11 Group) after May 1940 were not using 100 octane fuel routinely. I am particularly interested in learning the source of your statement that -

... it seems that there is evidence in May 1940 decision was made to stop existing conversion on the basis of the uncertainity of the supplies, and that around 1/4 of the Squadrons were supplied with this kind of fuel during most of the Battle.

- as this is appears to be contradicted by the decisions in the sources I have just cited.
 
Glider, interesting posts.

Re: December 1939 decisions.

I'd have to revisit the PRO to be definite about this, however:

My notes indicate that the position in December was that the 'roll-out' of 100-octane remained at ACAS' discretion, and this was issued in February subject to expenditure of 87-octane and replacement with 100-octane. The notes I have of the AoC-in-C of Fighter Command's memo on the issue of 12 December 1939 indicate that use of 100-octane was approved for the Hurricane, Spitfire and Defiant but I don't believe this amounted to execising the decision to begin using the fuel operationally, which seems to have remained at ACAS' discretion as I understand it. That authority seems to have been given in February and confirmed in May.

Let me know if I've misapprehended this.

In any case, the relevant file for that letter (PRO AIR 2/2434) should contain the rather interesting observation for some readers, made on 25 August 1938, that the RAF planned to supply 100 octane to all Spitfire and Hurricane bases.
 
Dont lose it boys, this is an intersting discussion

Your right, my wife who you will not be surprised to know is a teacher suggested I did some lines.

I must remember that everyone must produce everything and Kurfurst nothing
I must remember that everyone must produce everything and Kurfurst nothing
I must remember that everyone must produce everything and Kurfurst nothing
I must remember that everyone must produce everything and Kurfurst nothing
I must remember that everyone must produce everything and Kurfurst nothing
I must remember that everyone must produce everything and Kurfurst nothing
I must remember that everyone must produce everything and Kurfurst nothing
I must remember that everyone must produce everything and Kurfurst nothing
I must remember that everyone must produce everything and Kurfurst nothing
I must remember that everyone must produce everything and Kurfurst nothing
I must remember that everyone must produce everything and Kurfurst nothing
I must remember that everyone must produce everything and Kurfurst nothing
I must remember that everyone must produce everything and Kurfurst nothing
I must remember that everyone must produce everything and Kurfurst nothing
I must remember that everyone must produce everything and Kurfurst nothing
I must remember that everyone must produce everything and Kurfurst nothing
I must remember that everyone must produce everything and Kurfurst nothing
I must remember that everyone must produce everything and Kurfurst nothing
I must remember that everyone must produce everything and Kurfurst nothing
I must remember that everyone must produce everything and Kurfurst nothing
:lol: I feel better for that, now back to business as usual
 
Glider, interesting posts.

Re: December 1939 decisions.

I'd have to revisit the PRO to be definite about this, however:

My notes indicate that the position in December was that the 'roll-out' of 100-octane remained at ACAS' discretion, and this was issued in February subject to expenditure of 87-octane and replacement with 100-octane. The notes I have of the AoC-in-C of Fighter Command's memo on the issue of 12 December 1939 indicate that use of 100-octane was approved for the Hurricane, Spitfire and Defiant but I don't believe this amounted to execising the decision to begin using the fuel operationally, which seems to have remained at ACAS' discretion as I understand it. That authority seems to have been given in February and confirmed in May.

Let me know if I've misapprehended this.

In any case, the relevant file for that letter (PRO AIR 2/2434) should contain the rather interesting observation for some readers, made on 25 August 1938, that the RAF planned to supply 100 octane to all Spitfire and Hurricane bases.

I don't disagree with this. Clearly the use of the fuel was dependent on the availability of stocks being distributed. The authority was given in December for it to be used in Hurricanes, Spitfires and Defiants but that authority for General use was confirmed in May as the fuel had been distributed.
The letter of the 12th December 100 Octane Fuel Memo confirms that authority has been given to use the fuel, but general use is dependent on stocks having been put in place

I wasn't aware of the Feb documents and in my summary of the situation made a guess that there might have been some conditions attached but that I didn't know. From what you have said it looks like a confirmation was made of the December decision.
 
Glider,
here's what I have on the build-up to the use of 100 octane fuel

1935 - RAF now involved in 100 octane fuel, 29Jul35 it was decided that 95 or 100 octane fuel would be in general aviation use in 2 or 3 years time. The decision was the result of the visit to the US by one D R Pye of the Air Ministry who sent a long and detailed report of his findings to Vickers-Armstrong.

1936 - Samples of 95 and 100 octane fuel received from the US and the Asiatic Petroleum Company also offered their own 95 octane blend at the rate of 15 million gallons per annum. ShellMex and Anglo American offered the same quantities the following month.

1937 - By November, 3 RAF squadrons were using 100 octane fuel in their aircraft and a minute from the Air Ministry stated 'Deliveries under existing commitments will be, say, 5.3 million gallons per annum from March 1938 and 22.4 million gallons a year from March 1939 from all sources'.

1939 - Meeting held to discuss the issue of general release of 100 octane fuel for all RAF aircraft and what squadrons, number and type were to be supplied. The decision was taken to supply to 16 fighter squadrons and 2 twin-engined bomber squadrons by September 1940; the change-over to 100 octane was expected to result in the consumption of 3.1 million gallons per annum. The meeting also directed that a reserve of 250 million gallons was to be accumulated.

1939 - Secony-Vacuum (now Mobil) producing it at their Jersey plant. It was extremely expensive but the USAAC were using it in their aircraft in late 1939.

1939 - First trials of the fuel in a Spitfire took place at Rolls-Royce in Hucknall on 24Sep39 when K9788 fitted with a Merlin XII modified to burn the new fuel made its first flight. Take-off run reduced by 30yds. The cost of running a 100-octane Spitfire was £53 5s 0d dearer than running an 87-octane Spitfire per full tank expended (for those of you who are pre-decimal).

Initially, all 100 octane had to be shipped from the US and ran the gauntlet of the Atlantic U-boats, where a large number of supply ships were sunk but once refinement began at Abadan in Persia, the supply situation eased significantly.

There was a Supermarine report dated 16Feb38 concerning the Spitfire Mk I Production Bi-fuel installation, devised by Rolls-Royce to increase the power of combat engines.


Fighter Command would no doubt have recognised the fighting qualities of the Bf109-E by now and although what I have doesn't go as far as to actually say so, I would suggest that the threat posed by the Bf109-E coupled with the magnitude of the 100 octane fuel reserve would indicate that all participating (fighter) squadrons would be supplied with 100 octane fuel.

Just one point, three RAF squadrons were using 100 octane in 1937, what aircraft types would be likely to be using it that early?

That's to gavinb too, if you're still here.
 
Hello Gavin: Thank you for publishing your article The Narrow Margin of Criticality: The Question of the Supply of 100-Octane Fuel in the Battle of Britain. I found the article interesting and informative. Your research and work is appreciated.

What modifications to the engine were required btw?

Basically a modified boost control cut-out and new spark plugs.

ap1590b.jpg


This work was done on station at the time units were converting in March 1940.

no611-100oct.jpg


no74-100oct.jpg
 
Thank you. I assume this is maintenance level 3 stuff? Sounds like it anyways. Were they modified at the airfields or returned to repair center/assembling factories for these mods?
 
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