Messerschmitt Bf 109 G-6 Fuel Octane Marking?

[Johnson]

I'm just about to add the little yellow on white triangle that specifies the fuel next to the fuel filler at the top of the fuselage. The decals give 3 choices;

 

C3       B4      87 

 

I understand that C3 is 100 octane and B4 is 87 octane. The 109G-6 had the Daimler-Benz DB 605 A-1 engine and used 87 Octane fuel, so the 87 marking would be correct. But maybe B4 would be correct too, and why two markings (B4 and 87)?

 

Can anyone advise me which would be right? The Bf 109 G-6 I'm modelleing is Black (or Red) 8 of 2/JG302 in late 1943 or early 1944 at Malmi airport, Helsinki.

 

I'm sure I've seen this explained somewhere, but all my searches have failed to give me an answer!

 

Help appreciated!

[Troy Smith]

1 minute ago, Johnson said:

I understand that C3 is 100 octane and B4 is 87 octane. The 109G-6 had the Daimler-Benz DB 605 A-1 engine and used 87 Octane fuel, so the 87 marking would be correct. But maybe B4 would be correct too, and why two markings (B4 and 87)?

87 and 100 are octane ratings, C3 and B4 are for synthetic fuels,  made from coal I think.  I suspect that planes with the synthetic rating could use normal fuel, but perhaps not the other way round.

 

and, a bit more searching

https://forum.largescaleplanes.com/index.php?/topic/18841-luftwaffe-fuel-triangles/

 

"Kleinementor" - Fuel Markings and their meanings

 

Fuels 87 and 100 are the octane grades of petrol from natural crude oil. B4 and C3 are the (synthetic) equivalents distilled from (brown, low grade, lignite to sub-bituminous) coal oil.

 

The "N" marking was painted in white above or adjacent to fuel triangle markings in order to differentiate the two 100 Octane fuels: “N” being refined gasoline from "natural" crude oil with an octane level of 100 while “C3” was a synthetic artificial fuel distilled from brown coal with an octane level of 96.

 

Grade A3 = 80 Octane.

Light blue color. Yellow triangles, most times outlined in white, with black text “A3”.

 

Grade B4 / 87 = 87 Octane

Dark blue color. Yellow triangles, most times outlined in white, with black text “B4” over “87”, others with just “87”.

 

Grade C3 / 100 = 96-100 Octane

Dark green color. Yellow triangles, most times outlined in white, with black text “C3” over “100”, others with just “C3”. C3 is the synthetic equivalent of "100", but had an octane grade of 95/96. Rating it at 100 may reflect the inclusion of additives.

 

MW 50 = Octane 50 (MW = Methanol & Water: 50/50)

Variations of yellow or red triangles with the text “MW” over “50”.

 

 

from @David E. Brown

 

HTH

[Johnson]

Many thanks Troy, a very full and useful explanation. And a great link.

 

So, while I now understand what the markings mean, I still have to decide what my Bf 109 G-6 might have used; B4 or 87? I will plump for 87 as I've seen more photos of G-6s with 87.

 

Cheers,