On Sat, 14 May 2005, dyno wrote:

> True. There's also the inlet temperature effect; temp up octane
> requirment up.

Oops, no. Ambient temperature goes up, octane requirement goes DOWN, and
for the same reason that octane requirement decreases as altitude
increases: With both increasing altitude and increasing ambient
temperature, the intake air charge is less dense, therefore cylinder
pressure is lower, therefore tendency to ping is less.