Here's what
Oil: A study of war-time policy and administration by D J Payton Smith (HMSO 1971 part of the official war series) says about 100 Octane fuel pre- war plans and the so-called supply problems alluded to by Pips:
"The pre-war activity had been based on the assumption that United States supplies would be denied to Britain in time of war. In the event, as was shown, they remained available."
"100 Octane came into general use during the Battle of Britain..." confirming the All Commands memo issued on 7 August.
"...there was
NO anxiety in these early months of the war about the prospects of supply."