Verdict out on Top Tier gas

Dear Terry,
Is Costco gas as good as Tier One gas?
-- Richard

Dear Richard,
As I have written before, a group of refiners and manufacturers have agreed on certain formulations for detergents and other additives in fuel and labeled the fuel as Top Tier gas.

According to the group's Web site, retailers and refiners who produce Top Tier gas include QuikTrip, Chevron, Texaco, MFA Oil, Conoco, Phillips 66, 76, Entec Stations, Shell, Somerset Refinery, Kwik Trip/Kwik Star, Aloha Petroleum, Tri-Par Oil., Turkey Hill Minit Markets, Mileage Stations, Chevron Canada, Shell Canada, Petro-Canada and Sunoco Canada.

If your local Costco buys its gas from one of these suppliers, then it's Top Tier. The bigger question is whether Top Tier really improves or protects your car's performance. The verdict is still out.