I had a friend who logged his mileage based on where he filled up his car. Almost all the major brands resulted in no difference in mileage. The only brand where he consistently saw a decrease in gas mileage was the Arco brand of gas. He saw on average a 10% loss in gas mileage from Arco.
As for me I'm usually a shell guy. And really only because it's the closest station to my house.
As for me I'm usually a shell guy. And really only because it's the closest station to my house.