From: J. Forster (jfor@quik.com)
Date: Wed Oct 02 2002 - 14:44:11 PDT
Horrocks, Aaron wrote:
> The documents for my M38A1 say to use a gasoline with a minimum octane of 60.
> Wouldn't using premium with an octane of 91 be bad for my jeep in some way?
>
> Aaron Horrocks
The manual you quote says MINIMUM, not maximum.
Octane rating is a measure used to characterize the pre-ignition rating of
gasoline. If the rating is too low for the engine compression, the gas will
pre-ignite and cause knocking or worse. It is measured with a special, variable
compression, engine (without a spark plug) that is driven by an external motor.
The cylinder head is cranked down until the gas ignites by compression ignition,
like a diesel. The compression when ignition occurs is compared to pure octane
(which is a pure chemical, not a mixture of several chemicals) and that is the
octane rating.
As long as the engine stays the same, a higher octane will not give you more
power. It's largely a waste of money.
Flame away.
-John
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