We use Costco or Fred Meyer gas. Never had any issues and the mpg running average is 22.9, and that's mostly commuter/small trip driving. We're not on freeways that often or for that long.We prefer Costco or Sam's club gas. On a roundtrip from Chicago to Mt.Rushmore we tested Exxon, BP, Shell and Costco. With the conditions the same and running cruise control, we found a 10-15% reduction in gas mileage with BP, Shell and Exxon. And we prefer to support companies supplying American gas as much possible.