Petrol additives may increase petrol's octane rating, thus allowing the use of higher compression ratios for greater efficiency and power, or act as corrosion inhibitors or lubricants. Other additives include metal deactivators, oxygenates and antioxidants. Some additives are harmful and are regulated or banned in some countries.

Fictional additives

Additives

Racing formulations

Legislation

United States

Fuel additives in the United States are regulated under section 211 of the Clean Air Act (as amended in January 1995). The Environmental Protection Agency (EPA) requires the registration of all fuel additives which are commercially distributed for use in highway motor vehicles in the United States, and may require testing and ban harmful additives. The EPA also regularly reviews the health and net economic benefits of Clean Air Act policies. The act also requires deposit control additives (DCAs) be added to all petrol. This type of additive is a detergent additive that acts as a cleansing agent in small passages in the carburetor or fuel injectors. This in turn serves to ensure a consistent air and fuel mixture that will contribute to better gas mileage.