When i look at this picture:
i see that in june 1940 336000 tons of 100 octane fuel were supposed to be used
336000 tons would be 10584000 gallons
used by about 700 fighters that would be 151200 gallons per fighter
Average consumption for the Merlin mostly climbing would be about 75 gallons/h, so we get 2016 h flight time for each fighter.
Divided by 30 days that would give about 67,2 h a day flight time.
Now, where is the error?
Or are this only the stocks?