I will tell you what will work, and that is to use the catalytic converter heat to power the cars Air conditioner.
instead of powering the compressor off from the engine.
over the years I have always bought higher octane gas, because it does give better mileage, and when you compare the price of gasoline today versus the 10 to 20 cents a gallon for higher octane, it only makes sense.
however on short trips around town, most of your mileage goes down with stop and go traffic, and restarting the car for short trips.

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