The ongoing issue of finding a replacement for leaded avgas took an ugly turn recently after Cirrus advised owners that use of anything other than an “approved” fuel would likely invalidate the engine warranty. “Per Continental and Lycoming, only approved fuels may be used for an engine to be covered by warranty. As the GAMI G100UL fuel is a non-approved fuel per Continental and Lycoming, engines known to have run this fuel may not be covered by the OEM engine warranty. For specific details, please refer to the respective Continental and Lycoming engine warranty documents,” Cirrus said in a statement. “While some aspects of the initial Cirrus testing of the GAMI G100UL fuel are encouraging, other areas, including materials compatibility, remain inconclusive.”
At issue is that the GAMI fuel has not been submitted to the ASTM for “approval” but has received FAA approval in the form of a Supplemental Type Certificate that applies to virtually every spark-ignition aviation engine made.