[PAFirefighter11]

Originally Posted by Chris B.

I really haven't noticed a signifigant difference in gas mileage or how the car runs with between any major brand 91 octane or 93 octane. I've even done track days with Wawa 91 or 92 octane gasoline and had no issues. My 2008 Mustang GT was dynoed with 10% ethanol gasoline from the local Giant grocery store and it made good power for the mods it had.



I've heard the same things from other people that work in the petroleum industry currenly. Basically all the retailer custom additives are added after it comes out of the pipeline. Its all the same grade going in and each refinery doesn't deliver directly to the local distribution points. Your Sunoco 93 might have been made by BP or Valero, but have SUnoco's additives added to it.



In the winter its hard to find, but in the summer in the northeast some stations have it. Some even advertise it being Ethanol free and charge a few cents per gallon more for it.

Also http://pure-gas.org/ tries to maintain a list of Ethanol free stations.



Real world testing on may cars shows a gas mileage drop of 5-15% using 10% ethanol. The issue is the best air/fuel ratio for 10% Ethanol gasoline is different than the best air/fuel ratio for 100% gasoline.

Do you think when I get my car tuned the shop can tune it to work best on the 10% mix of ethanol since 95% of stations here run that?