The lowest octane rating your vehicle can handle without pinking is
said to be the best for it. Not just for mileage, but for carbon build
up.  My terminology may not be the greatest, but the higher the
octane, the harder it is to burn.  This is used in hi-compression
engines to prevent pre-detonation.

On 5/26/07, Anthony Egeln <regnsuzanne@yahoo.com> wrote:
> I can't explain it, but I also get better fuel economy with the 87 versus the 89 and 91 in my 2.1 wasserboxer....more is not always better.