Shell's not bad. I normally use Quik Trip, a regional station where I am. Gasoline brand can sometimes matter, too. I have had vehicles in the past that were brand sensitive, up to 2MPG better with more power to boot. Other vehicles didn't care. I even had two cars at one time, one only ran well on Shell and ran bad on Quik Trip, but the other one only ran well on Quik Trip but bad on Shell. I don't try to explain it, I just try the local stations and use whatever the car likes most. Can't do a one tank check either, you must run at least 5 tanks in a row with the first two tanks from a brand not counted to clear other fuel out, and average across all the tanks that count to see which runs best.