Octane grades
In the United States and Canada, gasoline octane grades are typically measured using the Anti-Knock Index (AKI), which is an average of the research octane number (RON) and the motor octane number (MON).
In both countries , the most common gasoline octane grades are:
•Regular octane gasoline: generally, this meets a minimum limit of AKI 87 (91 RON), although in some high-altitude regions that limit may drop to as low as AKI 85 (below 91 RON)
•Mid-grade octane gasoline: a blend of regular and premium grades; this grade generally has an AKI between 88 and 90 (92 and 94 RON)
•Premium octane gasoline: usually ranges between AKI 91 and 93 (93 and 98 RON)
•Ultra-premium octane gasoline: this grade typically has an AKI of 94 or higher (99 RON). Primarily available in Canada