Oktantall måles i AKI i USA.
United States: in the US octane rating is displayed in AKI. In most areas, the standard grades are 87, 89-90 and 91-94 AKI.[42] In the Rocky Mountain (high elevation) states, 85 AKI (90 RON) is the minimum octane, and 91 AKI (95 RON) is the maximum octane available in fuel.[43] The reason for this is that in higher-elevation areas, a typical naturally aspirated engine draws in less air mass per cycle because of the reduced density of the atmosphere. This directly translates to less fuel and reduced absolute compression in the cylinder, therefore deterring knock. It is safe to fill a carbureted car that normally takes 87 AKI fuel at sea level with 85 AKI fuel in the mountains, but at sea level the fuel may cause damage to the engine. However, since virtually all cars produced since the mid-1980s have fuel injection, 85 AKI fuel is not recommended for modern automobiles and may cause damage to the engine and decreased performance.[44] Another disadvantage to this strategy is that most turbocharged vehicles are unable to produce full power, even when using the "premium" 91 AKI fuel. In some east coast states, up to 94 AKI (98 RON) is available.[45] As of January, 2011, over 40 states and a total of over 2500 stations offer ethanol-based E-85 fuel with 105 AKI.[46] Often, filling stations near US racing tracks will offer higher octane levels such as 100 AKI.