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 plotting the Octane Number of Shell DTD 134 Spirit against the addition of Tetraethyllead (T.E.L.).
| Identifier | ExFiles\Box 27a\4\ Scan081 | |
| Date | 27th February 1933 | |
| SHELL DTD 134. SPIRIT OCTANE NUMBER (S30. @ 900 R.P.M. AND 150°C) CUBIC CENTIMETRES OF T.E.L. (PbEt4) PER IMPERIAL GALLON. HDoube 27. Feb. 1933 | ||