From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Letter discussing recommended oil viscosity, oil change intervals, and fuel type for a Bentley chassis B-78-EF.
| Identifier | ExFiles\Box 88\1\ scan0215 | |
| Date | 28th November 1935 | |
| Exptl. Dept. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}24/KW. 28th November, 1935. S.M. Swenson, Esq., Messrs. S.M. Swenson & Sons, 52, Wall Street, New York, U.S.A. Dear Sir, Chassis B-78-EF. Replying to your letter of November 15th. As you point out, the question of oils is largely one of consumption. The Bentley is a car which is produced to be able to be driven at sustained high speeds. For this reason an oil with a fairly high viscosity rating, i.e., Mobiloil BB, is recommended for Summer conditions. The oil for Winter conditions is dictated solely by starting requirements. You will appreciate that English conditions are such that a figure of 10° above zero is about the maximum which has to be catered for. In America, on the other hand, 20° below zero is not exceptional. We recommend that for Winter conditions you use an oil which suits your starting requirements, even if this necessitates going to S.A.E.10 viscosity. We agree with you that the lubrication is likely to be equally good with a thin oil as with one of a heavy viscosity. With regard to changing the oil, our practice is to do this at 5,000 miles, but we should never consider that it would be anything but beneficial to reduce this period to 1,000 miles. Referring to fuel, we run all our experimental Bentley cars at the factory on Ethyl, because this is the only fuel marketed universally which has the necessary octane value to prevent pinking with this high compression motor. | ||