In energy and air: the rating of the anti-knock characteristics of a grade or type of automotive gasoline as determined by dividing by two (2) the sum of the Research Octane Number (RON), plus the Motor Octane Number (MON); the octane requirement, with respect to automotive gasoline for use in a motor vehicle or a class thereof, whether imported, manufactured, or assembled by a manufacturer, shall refer to the minimum octane rating of such automobile gasoline which such manufacturer recommends for the efficient operation of such motor vehicle, or a substantial portion of such class, without knocking [Section 5(q), Philippine Clean Air Act of 1999] [Section 5(q), Philippine Clean Air Act of 1999]
Note: The term is alternatively referred to as Anti-Knock Index (AKI).