High altitude and low octane

[colin cohen]

Also remember, those of you with multiple cars that are not regularly
driven, that gasoline deteriorates quite quickly, especially in very warm
and cool temps.  Thus the 91 octane that you fill today (which itself may be
30 days since refining) will be 89 octane inside 3 months. This is one
reason for using the more popular gas stations.

The more modern chips are altitude and octane sensitive and can sense the
oxygen content of the detonated product to adjust the timing and the fuel
insertion. So even when you are not hearing detonation, your performance is
being effected by the octane deterioration.

This is a big problem for piston aircraft in hot 'n high conditions
especially at small airfields where gas sales are slow.

Colin