Due to the EUs unrestricted subintellectual green ideology warfare it is disputable whether the usual Autofuel STCs cover some of the current car gas station fuels. Typically the STC is issued on the basis of EN228, version of February 1999, but the eurocrats changed that to also put food and edibles in our tanks with EN228:2004 and EN228:2008.
Oil companies fight the bad chemical behavior of such mixed substances by restricting storage of fuel to 90 days after tap and adding additives, of which some fetch water and ethanol, thus rendering our basic ethanol tests virtually useless -> if you don't see a separation on the water test, it does not necessarily tell you there is no ethanol! Whether the water and ethanol fetched by additives is doing harm to the use in aviation is totally unclear.