[Paul Thompson]

Gentlemen,

I think that Ted has asked a very important pair of questions and I hope that forum members can bring their collective knowledge to bear to answer them directly.

There are two main points to clarify:

1. What aviation gasoline grades were used by the VVS and the Luftwaffe, respectively?

2. What were the MON and RON ratings of these gasoline grades?

I can contribute the following information:

1. I believe the main aviation gasoline type for Soviet combat aircraft during the mid and late-war period was 4B-78. The '4B' refers to the number of cubic centimetres (cm3) of an additive, usually 'R-9', per 1 kilogram (kg) of basic B-78 gasoline. The 'R-9' additive was an ethyl fluid which consisted of 55% Tetraethyl lead (TEL) and 35% ethylene dibromide, as well as 10% monochloro-naphthalene (MCN). In view of the large quantity of ethyl fluid used, 4B-78 was a highly leaded gasoline. This led to several problems, prominent among which was spark-plug fouling. The advantage of using the additive was that the effective octane number rose to 95, so the fuel could be used in higher performance engines with a higher compression ratio.

I believe that the majority of the 'R-9' ethyl fluid, or at least the majority of the Tetraethyl lead that was the main component of this fluid, was delivered to the USSR via Lend-Lease. Therefore, Lend-Lease was essential to all Soviet stocks of high-octane gasoline, not just the Allied gasoline grades that were imported in bulk.

2. Soviet industry used Motor Octane Number (MON) ratings, a method which produced lower octane ratings for the same fuel than the Research Octane Number (RON) would have done. Thus, the B-78 gasoline mentioned above had a MON rating of 78 but a higher RON rating. With the 'R-9' additive, as 4B-78, the gasoline should have had a rating of 95. This could vary significantly in practice as the fluid was often mixed with the basic gasoline in the field, where accurate measuring equipment was absent.

Regards,

Paul