A new study from Market Force reports that Costco and Sam's Club are America’s favorite places to get gas, making it the second year in a row that wholesale clubs have beaten conventional gas stations. QuikTrip, Wawa and RaceTrac rounded out the top five. Broken out by region, Costco ranked first in the West, Speedway in the Midwest, Shell in the South and Sunoco in the Northeast. Overall, Chevron scored highest for brand reputation. Market Force, based on Boulder, Colo., calculated rankings on total votes, and then factored in the number of locations for each chain for weighted results.