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).
Graph of constant speed petrol consumption (MPG vs MPH) for a 7 B.V. engine, comparing different needle types and gear settings.
| Identifier | ExFiles\Box 147\5\ scan0159 | |
| Date | 29th June 1939 guessed | |
| M.P.G. CONSTANT SPEED PETROL CONSUMPTION - 7 B.V LB1 NEEDLES [TOP GEAR] OVERDRIVE [LB1 NEEDLES] R.R.X NEEDLES [TOP GEAR] M.P.H. | ||