To me it appears there were two fuel problems, and they were over 1 year apart.
The early problem (British 20% min and US 2% max) went away in late 1941 or early 42, before P-38s showed up in England.
The US had already agreed to use much higher amounts of aromatic compounds for 100/125 fuel and test batches should have been sent to all engine makers to try to catch problems.
The 100/125 joint specification didn't last long, a few weeks or months and was superseded by the first 100/130 specification.
I don't know if some people in the US were using "British fuel" as a shorthand for the 100/130 fuel. Or were using "British fuel" as shorthand for a blend favored by the British. Agreements on fuel were not easy. USN and US Army didn't agree on amounts of certain compounds let alone agreeing with the British. The British were pushing aromatic amines to enhance rich mixture response. Shell (British) chose monomethyl amine to concentrate on, shortened to methyl amine. This worked well in for rich mixture but gave no benefit to lean mixture, in fact it sometimes degraded lean mixture. British in early work were more interested in better rich mixture performing fuel than increase production. US was interested in lean mixture cruise so there conflicts right away. Standard Oil of California wanted to use Xylidine instead of methyl amine.
The late 1942 fuel standard for 100/130 is always listed as going to 4.6cc per US gallon for lead but other changes are not given except to say that more heavy aromatics were allowed. It was this fuel that gave the problems with the P-38s and it was anticipated that the heavier aromatics would give problems and small batches of fuel were manufactured and give to engine makers to see what problems there might be. But in short histories of fuel they never say what these heavier aromatics are. Turns out the radials with their short intakes didn't have the same problems as the Allison and British problems or lack of problems are not recorded by the most popular writer.
It was found that this type of fuel would separate out and puddle in the intake manifolds of the Allison engines and the "Madam Queen" intakes were developed to counter it, on ALL Allison engines not just the P-38s although little or no trouble seems to have occurred in service.
P-38s only operated in England for a short period of time in 1942 before going to North Africa. They didn't go back to England until the Summer of 1943.
As I have said before, by this time the US 100 octane fuel with 2% is long gone. But there was a fuel that was going to give problems in 1942/43 and it was known and things were being done, maybe not fast enough. Depending on who was writing reports/letters there may certain blend/s of fuel that some people called "British fuel".
In the US there was quite a controversy over using Xylidine and the Navy wanted no part of it. They thought that water injection was better solution than using Xylidine in the fuel to push past the 100/130 fuel limit and finally refused to accept any fuel that had Xylidine in it. The Army wanted Xylidine for liquied cooled engines and in fact even the army was not in 100% agreement. Wright field was in favor of limited use but was opposed to general use. Xylidine was used in the 100/150 fuel but not 115/145?
I am not saying there were no letters talking about "British fuel". I am not saying there were no problems with the P-38s with some of the fuel the P-38s were using in England in 1943 (or even in other places in fewer incidents). I don't know if there are not some terse notes about "Army" and "Navy" fuels floating around in late 1943/early 1944.
But what was "British fuel"? and how did it differ, especially considering all the different possible blends that could be involved.
Any P-38s, P-39s or P-40s using WEP power in the fall of 1942 (or unauthorized in mid 1942) was using 100/130 or perhaps 100/125, they sure were not using 100/100 US 1940 fuel without blowing up the engines. I am not sure anybody got the 100 octane fuel from Burma, Malaya, DEI back to lab to be tested.
I am also unclear about how re-jetting fixed the problem. I may not have the needed knowledge but doesn't jetting simply mean either leaning the mixture or richening the mixture?
Perhaps the mixture was too rich for cruise allowing the puddling to happen? But changing the jets should not stop heavier compounds from separating out or cause lead to not separate out either?
