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).
Comparison table of performance metrics from two R.A.C. tests, one for a Napier and one for a Rolls-Royce vehicle.
| Identifier | ExFiles\Box 81\1\ scan0048 | |
| Date | 1st June 1920 guessed | |
| Particulars of two R.A.C Tests. 6-cylinder Napier 59.9 h.p. R.A.C. Rating. 6-cylinder Rolls-Royce 48.6h.p. R.A.C.Rating. Route taken: London to Lands End to John O'Groats to Edinburgh and back to London London to Edinburgh and back. Petrol Consumption: 23.9 m.p.g. 53.2 ton m.p.g. 24.32 m.p.g. 57.07 ton m.p.g. Speed on Brooklands: 77.1. m.p.h. 78.26 m.p.h. Windage: 10.3 sq. feet. 13.01 sq. feet Total weight with passengers: 4990 lbs. 5257 lbs. Gear Ratio: 3 to 1. 2.9 to 1 Bore and stroke of engine: 5 x 5 inches. 4½ x 4½ inches. C. Johnson | ||