Now that the supply of Benzole to the motoring public has ceased, considerable interest attaches to “Octol,” an anti-knock medium made by the High Flash Petroleum Co., 40a, Parsons Mead, West Croydon, Surrey (tel.: Croydon 7634). This new preparation is sold in 5 and 10-gallon drums, at 15s. a gallon, and is coupon-free. We are assured that it does no harm to the engine and that the addition of from 2½ to 10 per cent. to Pool petrol gives the same immunity from pinking as 50/50 petrol-benzole. The makers claim that 10 per-cent. “Octol” completely cured pinking in a 2½-litre Riley with its ignition in advance of the maker’s recommendation, and that an M.G. Magnette with a compression-ratio of 8.125-to-1 was cured by adding 5 per cent. “Octol.” For our own test we used a “special” with a 10-h.p. s.v. engine, having a compression ratio of nearly 9-to-1 and an iron head. Two-and-a-half per cent. had practically no effect, 5 per cent. muffled the pinking which occurred when accelerating up to 44 m.p.h. in top gear, and 10 per cent. almost completely cured it, 12½ per cent. would probably have banished pinking altogether. Fuel consumption appeared to be unaffected but there was a suggestion that a slight increase in jet size would have improved carburation on the 10 per cent. mixture.
“Octol” is expensive, but as only small proportions are required to achieve the same effect as 50/50 petrol/benzole at about 5s. 6d. a gallon, this preparation, especially as it is unrationed, will be of considerable interest to those whose cars emit an anvil-chorus whenever the throttle is opened under load, and to competitors in this year’s sports-car races in which variations from pump fuel are allowed.—W. B.