[DML] Re: Premium Gasoline

["BRUCE BENSON" <delornut@xxxx>]

After reading the threads on fuel octanes I thought I might add my two
cents. The higher the octane rating, the less volitale the fuel. That means
higher octane fuels don't light off as quickly nor as hot as lower octane
fuels. That is why they resist pre-ignition or pinging. If an engine is
designed to run on low octane fuel and is fed a diet of high octane fuel it
can, in a sense, become dependent on high octane. The reason is the lower
combustion temps resulting from high octane ratings can, in time, produce
carbon deposits in the combustion chamber which raise the compression ratio.
At some point the compression ratio gets high enough to mandate high octane
fuel to prevent the pre-ignition. The point here is nothing is gained using
high octane fuel in a low compression engine. The DeLorean shop manual
recomends 91 octane fuel with a compression ratio of 8.8:1.

Bruce Benson