In the United States all motor vehicle gasoline is unleaded and is available in several grades with different octane rating; 87 (Regular), 89 (Mid-Grade), and 93 (Premium) are typical grades. At high altitudes in the Mountain States and the Black Hills of South Dakota, regular unleaded can be as low as 85 octane; this practice has become increasingly controversial, since it was instituted when most cars had carburetors instead of the fuel injection and electronic engine controls standard in recent decades.