Re: MPG and Octane

[jkerouac@xxxxxxxxxxxxx]

Karl,
   We all use the fuel of our choice.  I find that 20+ years of BMW driving
shows that higher octane fuel always gives better gas mileage, in my cars,
the way I drive.  Your cars and your driving style may give difference
results.
     In cars without adaptive motronics, lower octane can be run by manually
retarding the spark timing at the distributor and/or the cam timing at the
cam gear, and with different carburetor jets.
     The cars with adaptive motronics can run on lower octane with the
adaptive window reducing the spark advance and cam timing as needed.
Whether due to lower advance or any of many possible operating parameters,
on all the BMWs I've owned the gas mileage is lower in all cases with lower
octane gasoline.
     For economy testing, the results are most accurate if the engine is in
its best state of tune.

     I hope my posting will generate digest subscriber's responses giving
actual experiences rather than suppositions based on partial theory for
which there are equally valid sounding counter arguments.

     So please tell the digest what you drive, how it is tuned, what gas you
use and what your fuel economy is with different gasolines.

'Happy Motoring
'jk

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