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 the complexities and benefits of using thinner oils for motor car engine lubrication.
| Identifier | ExFiles\Box 145\3\ scan0062 | |
| Date | 21th November 1936 | |
| Copy AD/MHR.{M. H. Rigby} Duckham House, 16, Cannon Street, E.C.4. 21st November 1936 A.F.Sidgreaves Esq. Bentley Motors (1931) Ltd. 16, Conduit Street, W.1. Dear Sidgreaves, Your letter of the 12th. November is welcome not only because you ask me to send samples for test but because you indicate the adoption of much thinner oils, a practice which I as a scientist, have long advocated, but as a man with some 38 years' experience of commercial lubrication, have been nervous of urging in the case of motor car engines, and this because they call for a compromise, not only to safeguard a number of parts of very varied requirement, but also on account of the very deficient attention afforded by most owners. A huge turbine with its regulated forced feed, its cooling, its regular performance and its unceasing expert attendance is the simplest of all movers to lubricate - a thin highly refined oil of no affinities for metals or for water fills the bill, but in a car you have forced feed in one part and splash and self-creeping feed in others, whilst loads, temperatures and play due to wear are ever-varying factors and the attendance is mostly nil. So a thin oil of no affinities will not, in a car, give you the margin of safety - it must have a certain excess in viscosity, an affinity for metal surfaces and a creeping or capillary penetration; with these two last well developed, the viscosity can be much reduced. Only last week one of the most important companies put their fancy for thinner oils before me, confessing they were nervous about it and asking our co-operation; if your people would also take us into their confidence, we should regard it as a privilege. The metal used for the bearings is of importance, e.g. fatty oil is inadvisable with lead bronze. By the way, a minor matter always troubles me and that is that working temperatures of the engine vary far less between summer and winter than do the atmospheric, but just because of a few minutes of starting trouble, some car makers advocate a huge reduction in viscosity. Again, look at the variations in viscosity at, say, 140° F.{Mr Friese} of the various oils | ||