Gasoline Detergent Additives

Are they worth the extra money at the pump?

Prepared by the SAE Fuels & Lubricants Council

Today's cars and trucks have very sophisticated fuel injection systems and engines, to inject precisely the right amount of fuel into the engine at exactly the right time, and burn it efficiently to provide optimum vehicle emissions control, performance, fuel economy, and durability. Deposits that form on fuel injectors, intake valves, and in the combustion chambers can interfere with proper operation and cause problems.

The U.S. Environmental Protection Agency has recognized the importance of preventing or at least minimizing deposits to maintain low emissions. Therefore, EPA as part of the Federal Clean Air Act requires that essentially all automotive gasolines in the country contain deposit control (detergent) additives that will limit fuel injector and intake valve deposits, as demonstrated by standardized vehicle tests. This level of deposit control is adequate for some vehicles under some operating conditions. However, some gasolines tend to form more deposits than others, and deposit formation also is affected by vehicle operating conditions and by the design of the fuel injection systems and engines.

Although EPA's minimum detergency requirements are beneficial, they do not satisfy the needs of all vehicles. Many oil companies have chosen to provide more than the minimum required amount of additive. These include some small, independent marketers as well as some major marketers, and these marketers often advertise their fuel's improved detergency. Unfortunately, many consumers may not be aware of which fuels have better detergency. Even with that information, however, most consumers are not able to evaluate the claims made by marketers.

To promote improved gasoline detergency and provide a means for fuel marketers to distinguish themselves from their competitors and advertise this fact to consumers, several major automobile manufacturers introduced the "TOP TIER Detergent Gasoline" program in 2004. This program sets tough standards for controlling deposits on fuel injectors, intake valves, and combustion chambers, as well as preventing problems that are sometimes caused by improper use of additives. The program is voluntary and is open to any U.S. and Canadian fuel marketers. Companies wishing to participate must demonstrate, using specified test procedures, that they meet the requirements of the program. Importantly, they must agree that all grades of their gasoline (not just premium, for example) meet the requirements at all retail outlets within the country (U.S. or Canada, as applicable). Once approved by the OEM Sponsors those marketers can then advertise that they comply with the TOP TIER Detergent Gasoline program, and this information is often posted at gas stations. A list of TOP TIER Detergent Gasoline marketers can be found at and includes a number of small marketers and some (but by no means all) major oil companies. Additional information recommending the use of TOP TIER Detergent Gasoline can be found in most OEM sponsors owner's manuals.

It is important to note that the absence of a gasoline marketer from the list of TOP TIER Detergent Gasoline participants does not necessarily mean that the marketer is using only the minimum EPA-required amount of detergent additive. For one reason or another, that marketer may simply have decided not to participate.