The relative volumes of production of the two grades cannot be accurately given, but in the last war years the major volume, perhaps two-thirds (2/3) of this total has the C-3 grade. Every effort was being made toward the end of the war to increase isoparaffin production so that C-3 volume could be increased for fighter plane use.
Technical Report 145-45 - The Manufacture of Aviation Gasoline in Germany
Most Bf109s used B4 fuel. The BMW801 of the Fw190 required C3 fuel. There was about equal numbers of each in Luftwaffe service, late war.
The 2/3rds of production was C3 doesn't make too much sense to me. The DB601/DB605/DB603, Jumo 211 and Jumo 213A all used B4 fuel throughout the war apart from the following exceptions;
DB601N in a short period between the middle of 1940 to the middle 1941 when it was replaced by the DB601E which used B4.
Although DB605ASM and AM were designed for B4+MW50 the apparently used C3+MW50 from about April 1944 till some period in late 1944 when the DB engines again reverted to B4+MW50. The problem apparently being that if the engine ran out of MW50 while in over boost severe engine damage could result. The obvious solution would have been a flow switch in the MW50 line that operates some kind of solenoid, motor or device to cut out the over-boost. I don't fancy the prospects of getting that kind of system working reliably and in production all that easily. One could try a level switch but then we are doing maneuvering, negative G etc. Perhaps the C3 also helped keep the boost up until improved spark plugs came along, but even late war DB605DB were restricted to 1.45 ata when only B4 was available and no MW50.
The main users of C3 fuel was the BMW801D engine of the Fw 190 yet the DB and Jumo engines were much more produced as were there customers Me 109/Me 110/Me 210/Me 410/Ju 88/Ju 87/He 177 while all the transports, Fw 200, used B4.
Perhaps some airfield defense units used C3 in the Fw 190D9/D13 in 1945. We seem to have delivery documents.
The fischer-tropsch.org site has a tremendous amount of information. Most interesting are British intelligence files on analysis of German fuels taken throughout the war from drop tanks, crashed machines, captured fuel supplies etc. Unfortunately they are not indexed but simply pdf image scans taken from microfilm and one has to find a spare 2-3 hours to go through them. There is USAAF and USN analysis but their interrogations didn't begin until after WW2.
These reels show several improvements in C3 fuel grade which they always refer to as "green dyed" fuel. They note a big jump in early 43 which they assume will be for a new type of engine not yet in production that is able to exploit the high rich mixture response. The Jump seems to have been from 94RON/115PN to 97RON/125PN according to the British testing methods, they seem to have reached 97/130 but it has to be noted that allied 100/130 was really 102/130 while 150 was more like 104/150 or 110/150. (The US latter introduced a genuine 115/145)
Unfortunately in many cases they do not bother with a PN test and only do the easier RON test. In most cases they don't even bother with a RON test and simply distill of the fractions, the experienced petro-chemists only testing further if they see something unusual.
The micro film reels were supposed to be destroyed: the US government or US petro chemical industry apparently didn't want useful information about how to synthetically produce gas or coal based gasoline freely available. Fortunately they survived at Texas AM university by accident.
Early 1944 the allies started attacking the German fuel industry, repeatedly, this created severe reductions in production and raised great concerns. C3 fuel was of even greater concern as it required more production facilities and having read plenty of books on the Fw 190D/Ta 152 I can say they all say that the Jumo 213 and DB603 engines were all switched to variants that could use B4+MW50 instead of C3 but note even the methanol for MW50 could be in short supply; synthesis was not too difficult as the catalysts were very precise but it still required a coal gasifier.
Towards the end of the war much German fuel was often just distilled of coke or coal tars (benzol process) due the damage to the synthetic plants. When one says "2/3rds of the fuel was C3" one is referring to greatly reduced production. That 2/3rds of production was C3 before or during 1943 or even early 44 doesn't make sense as there wasn't a German Airforce fleet to use that much C3 fuel.