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).
Table comparing constant speed petrol consumption for various vehicle models.
| Identifier | ExFiles\Box 147\5\ scan0182 | |
| Date | 27th June 1941 guessed | |
| CONSTANT SPEED PETROL CONSUMPTION. M.P.H. | B.II | WRAITH | PH.III | 1939 Century BUICK | 6)cyl. OLDSMOBILE. 20 30 | 25.0 | 21.5 | 14.5 | 18.0 | 25 40 | 23.0 | 20.2 | 13.7 | 16.8 | 23 50 | 20.5 | 18.0 | 12.5 | 15.5 | 20.5 60 | 18.0 | 15.5 | 10.6 | 14.2 | 18.0 70 | 15.3 | | 9.0 | 12.5 | 15.3 80 | ||