[WardL]

Particularly so in California, the base gasoline is the same. The difference comes from the additives put in the fuel when it is branded at the truck rack. Chevron has their Techron, Shell with their Nitrogen enriched. I believe gasoline supplied in the Shasta area comes out of the terminal in Chico where the Shell, 76, Chevron, ARCO, Valero, Safeway, etc, regular gasoline is stored in the same tank. Premium gas is stored in another tank for all brands. When the delivery truck fills up for Chevron, they add the Techron, etc. The EPA requires all fuels to have additives to keep an engine clean. All gasolines have the additives. Some areas of the country have segregated fuels, but not many.

It is impossible to scientifically tell the difference between one expensive tank of gas and the next tank of cheap gas. Your mind will play tricks on you and you THINK you can tell a difference, but you really can't. It is really interesting how advertising can influence your mind!

The expensive brands do add more additive that will keep your engine cleaner over many thousands of miles or more. But California gasoline is so clean already due to the state requirements, I'm not sure that statement really even applies in California.