Of course all of us can look it at different the evidence posted at angles, but a very definietive claim like this should be backed up by very definietive sources speaking in no uncertain terms. Certainly if 100 octane fuel was used in such an uniform manner as some posters claim, there should be evidence easily found for this.
This can be applied to the 1.98ata boost used on the K-4. Unfortunately there has been no conclusive proof that 1.98ata boost was used by the 4 Gruppen authorized to use the 1.98ata boost, only speculation.
The only so called proof is:
a/ A German document (Lw.-Führüngstab, Nr. 937/45 gKdos.(op) 20.03.45) saying 'boost increase to 1.98 ata'.
The problem here is there is no primary documentation presented for 1.98 ata boost useage.
b/ a secondary source saying there was 284,000 liters (62417 Imp Gal) of C3 on Bavaria airfields.
The problem here is the airfields where there is C3 fuel are not specified. C3 at airfields where the 4 Gruppen authorized to use 1.98 ata boost are not based is not of much use to those K-4s.
Oliver Lefevre:
"And even after the clearance only few gruppen got it because of shortages due not only to C3 production but also to C3 delivery to the units."
"From other documents I know that C3 and B4 had severe quality problems beginning in late 1944."
"At least DB documents underlined the need for cleaner fuels than those in use at that time."
from Douhet: Still Relevant Today
"It wasn't until 1944, when Major General Ira Eaker, Commander Eighth Air Force, changed target priorities that strategic bombing started to have the desired effect on German war production. General Eaker identified two major target groups:
(1) The Sources of Energy Group (coal and synthetic oil);
(2) The Transportation Group (canals and railways). (6:285)
Once the major emphasis of strategic bombing was moved to these two target groups, measurable
results were seen. The air objective was to disrupt all rail traffic in Germany. By October 1944, rail traffic was nearly paralyzed.
Essen Division car replacement of coal which had been
21,400 daily in January 1944 declined to 12,000 in
September. By November delivers of coal to factories
in Bavaria had been reduced by nearly 50 percent. By
January 1945 coal placements in the Ruhr district were
down to 9,000 cars per day. Finally, in February well
-nigh complete interdiction in the Ruhr district was
obtained. Such coal as was loaded was subject to
confiscation by the railroad to supply locomotive fuel
coal. As mining continued at a higher level than trans
port, coal stock reserves increased from 415,000 tons
to 2,217,000 and coke stocks increased from 630,000
tons to 3,069,000 in the same 6 months (7:63)
In May 1944, preliminary attacks were made on the larger synthetic oil plants. These plants had been producing 316,000 tons a month; in June their output fell to 107,000 tons, and in September to 17,000. Aviation fuel production also dropped from 175,000 tons to 5,000. These attacks dealt a crippling blow to the munitions and explosives industries, and reduced the supply of synthetic rubber to about one-sixth of its war time peak of 12,000 tons a month (6:286)."
Not sure of the source but believe it is Oliver Lefebvre
A 1944 K-4 should be equipped with a DB605DM at 1.75ata since delivery of DB605DB did not occur until mid january 1945. The DC which were basically the same engine were to be delivered in the DB configuration until the 1.98ata boost was cleared.
By february 1945 orders were issued to begin tests of the DB605DC set to 1.98ata, and plans were made to convert existing squadron with DB605DB engines to DB605DC standard.
What is not known is to what extend it was done before war ended as we do not know whether testing was positive or negative and if the former at what time the DC was considered operational.
Just to correct some confusion about the C3 issue.
When first issued the DB605DM/ASM/AM were required to use C3 fuel, and it was not until some time that those engine were cleared to use B4 as well. It required some timing adjustement as well as some nerves since a failure of the MW-50 system in such a configuration broke the engine almost immediatly.
So it's quite normal to see C3 markings on a K-4 or G-10 it does not mean by anyway that the a/c is actually using a DB605DC.
for instance almost all K-4 of the 330xxx-333xxx batches wear a C3 triangle while the later 334xxx batch a/c are wearing a B4 triangle.
It flew but to what extend tests made by the II/JG11 with the DB605DC at 1.98ata were positive is not known at this time. Early reports of the 1.90ata test underlined spark plugs troubles as well as mechanical troubles and the insufficient cooling of the 109. Those troubles prompted the decision to deliver all DC engines set to DB standard at 1.8ata.
All those events took place in february, and plans were made to clear it for operational use as underlined by planned unit equipments listing. Now it remains to be seen to what extent it was done before the war ended.
One often sees a photos of K-4s with a C3 fuel decal. This does not mean the K-4 used 1.98 ata boost. Besides, one of these photos is an K-4 from 11./JG3.
c/ 116000 litres (25494 Imp gal)) of C3 fuel in Italy as of April 23 1945 and only 7000 litres (1538 Imp Gal) on May 1 1945.
This is stock available to the Kommandierender General der Deutschen Luftwaffe in Italien for all his units, German and Italian. The Germans decided who got the fuel, the Italians had no control over this.