I heard a smog inspector interviewed on the radio about some easy tricks to passing smog. One of the aspects I found interesting was his thoughts on gasoline brands. It was his belief that shell and chevron gas was the best, and gave cars significantly better gas mileage. So even if it cost 10% more, he thought you may get up to 20% better mileage. I too have noticed a difference in mileage between arco and the rest. He also said, he has failed cars with arco, who have come back with shell and passed. So, take that anecdote for what it is worth.
