Does a Petersen STC allow for the use of 82UL?
A. Yes and no, depending on the engine. For an engine originally certificated for 87 octane or less, 82UL may be used in conjunction with a Petersen STC. Fuel placards available from Petersen Aviation differentiate between those airplanes that are or are not capable of using it. The original octane rating of the engine is what dictates whether or not 82UL may be used. 82UL must not be used in engines that are approved for 91 octane mogas. The octane rating of 82UL is too low for this type of engine. So for example, the 150hp 0-320 which is STC’d for 87 octane (minimum) mogas may also use 82UL. However the 160hp 0-320 must not use 82UL because the higher powered version of this engine is approved for a minimum octane rating of 91.
