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).
The investigation into excessive oil consumption for a Bentley B.244.GA at 15,000 miles.
| Identifier | ExFiles\Box 131\4\ scan0360 | |
| Date | 7th July 1937 | |
| To Rm.{William Robotham - Chief Engineer} from Rm{William Robotham - Chief Engineer}/GWH.{George W. Hancock - Head Chateauroux} c. Hs.{Lord Ernest Hives - Chair} Levallois, France, July 7th.1937 BENTLEY - EXCESSIVE OIL CONSUMPTION. B.244.GA. - 15,000, miles. This car has recently been fitted with L. rings to the pistons to overcome excessive oil consumption. The owner still maintained that no improvement had been made i.e. two litres per 100 KMS. We therefore have carried out a test today. The results verify his remarks. 88 miles test. (Tyre punctured and petrol pump gave out during test) .44 gallons of oil used. Engine revs. max. 4,000 Time 1 3/4 Hours. Oil pressure 35 lbs. Oil consumption 200 M.P.G. Average speed 50 M.P.H. The cylinder bore wear is an average of .0015" max. .0025" XL. oil used on all tests. The cylinder bore wear as I have stated on the cars which have been dealt with, has not been excessive and with ordinary driving, such as is possible in England, would not give heavy oil consumptions. I have come to the conclusion that the following is the cause of the heavy oil consumption. (1) Standard piston clearance at high speeds allows high velocity period to develop in the piston transmitted from the crank-shaft. (2) Pistons rings develop flutter. (3) High oil pressure giving more oil thrown on to cylinder walls cannot be dealt with, in view of No.1 & 2 conditions. (4) The fitting of an L. ring to an old piston is not right in my opinion, as the groove is worn and allow flutter of the ring to take place. continued | ||