Rob Schwartz coldinvt at
Fri Apr 20 20:52:11 PDT 2007

I always run the lowest octane recommended by the mfgr.  "Octane ping" can
be caused by using lower octanes in higher compression engines (>10:1
maybe?).  The lower octane is subject to flash from the compression and
residual heat alone, before the spark happens... pre-ignition.  Feeding high
octane fuel to a lower compression environment certainly can't help and may
actually affect performance/efficiency.

The VFR is always happy on 87, as recommended in the manual.  I'm not sure
what the GPZ calls for.  Out in CO they sell 86 right, Scapp?  I'm sure you
don't need as much octane at higher altitudes.  With less oxygen, the lower
flash point of lower octane could be beneficial.

My .02 (.008 with the exchange),

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