 From March 1940 increasing quantities of 100 octane fuel, imported from the US, became available.This meant that during the defensive battles over Dunkirk the Hurricane Is benefited from an allowable increase in supercharger "boost" from 6 lb to 12 lb without damaging the engine.With the 12 lb "emergency boost", the Merlin III was able to generate 1,305 hp (973 kW) in a five-minute burst.