just get a BP (not a sponser) card and get 5 cents off for each dollar you spend on gas, right now prm gas is 4.02 per gal in south florida, my cost with my bp card at a bp station is 3.80 per gal. save that way if you want to use prem.
off subject but another thing that i do, (my ID was stolen 4 years ago) is when i buy gas i end the cents in the same as the dollar, example if my gas is 40 dollars i end the pump $40.40 if 27 i end it $27.27 and so on this way when i get my bill and there is a amount for say 21 dollars and 70 cents $21.70 I know i didn't buy that and i call and despute it.