All gasoline retailers in a given market sell the same grade and quality fuel, as the government has very precise standards for octane and other gasoline characteristics. The only difference between different brands of fuel is the detergent additive package. Since 1995, the federal government requires that all gasoline sold in the U.S. contain detergent additives. These additives must be EPA-approved, and the government specifies the amount based on what it takes to keep engines free of deposits. Because it's a performance-based requirement, over the years the fuel suppliers have figured out ways to use less of these expensive additives to achieve the government standards. All Costco gasoline contains detergent additives in the amount necessary to meet these requirements.
Recently, several automakers (BMW, GM, Toyota, and Honda) announced their new "Top Tier" standard for gasoline, as they believe the government additive requirement is too low. They invited gasoline manufacturers to certify their fuel to this higher standard, and several have done so. Other major oil companies, such as BP, declined as they believe the auto manufacturers are simply trying to reduce their warranty claims. To achieve this voluntary "Top Tier" designation, all the fuel sold in the U.S. must meet the higher standard. Costco cannot currently do this as we buy from a variety of refiners and distributors around the country and do not own our own truck terminals where the additives are blended with the fuel.
Nor is it certain how much additive is really necessary to keep an engine clear of deposits. The fuel detergent is only one component, as anything that causes incomplete combustion will lead to valve deposits and fuel injector clogging. It's easy for an auto mechanic to simply declare the problem is the gasoline. So the science is uncertain, and the industry response is certainly not unanimous. Regardless, we are actively researching the issue directly with the various additive manufacturers. We are hesitant to raise the cost of fuel to our members without first understanding if this is simply a way for some brands to charge more for their fuel. We do know that we sell a tremendous amount of fuel with very few complaints.
Costco only buys fuel from reputable suppliers, and we do a very good job of maintaining our tanks and pump filters to assure clean fuel is delivered to our members. If you remain concerned about fuel deposits, Costco sells a four-pack of Chevron's Proguard fuel injector cleaner in our warehouses for about $10, or $2.50 per bottle. It's much less expensive to use a bottle of this occasionally than to buy higher priced fuel every time you fill up. Any auto parts store has a shelf full of similar products.
Again, all Costco fuel contains detergent additives sufficient to meet the government standards. As with anything we sell, our fuel is 100% guaranteed.
