"Bob Fry" wrote in message
...
"Scott" == Scott writes:

Scott One thing I think "might" be a concern is that burning
Scott 100LL (can't get 80 octane avgas these days) in an engine
Scott built for 80 octane is the extra heat.

Eh? Where's this "extra heat" come from? There is no practical unit
energy difference between different octane fuels.
--


Exactly. "Octane" is, by definition, a measure of a fuel's resistance to
knock under specific conditions. "High Octane" fuel does not burn any
hotter, generate any more power, or improve your fuel economy (note: see
exception below). Higher octane fuel lets the engine designer use a higher
compression ratio, or more spark advance, etc. without triggering knock. It
is the compression / spark changes that result in more power, etc.

Exception: _Some_ automobiles have sensors that detect knock and will adapt
the spark advance to match the fuel properties which will then improve your
fuel economy.

--
Geoff
The Sea Hawk at Wow Way d0t Com
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