The Federal Aviation Administration regularly publishes Special Airworthiness Information Bulletins about aviation safety issues, these are mandatory reading material for pilots and aircraft owners.
This SAIB alerts you of an airworthiness concern where you could have alcohol (ethanol or methanol) present in the automobile gasoline on any General Aviation airplane.
Excerpt from the document:
This Special Airworthiness Information Bulletin (SAIB) alerts you of an airworthiness concern where you could have alcohol (ethanol or methanol) present in the automobile gasoline on any General Aviation airplane type certificated (TC) to use automobile gasoline or with automobile gasoline supplemental type certificates (STC).
Fuels have to conform to a specification in order to be approved for use in type certificated aircraft. The American Society for Testing and Materials (ASTM) developed specifications for automobile gasoline as well as aviation gasoline. These specifications are ASTM D 910 and ASTM D 6227 for aviation gasoline and ASTM D 439 or ASTM D 4814 (latest revision) for automobile gasoline.
To continue reading see the pdf below: