I believe super unleaded fuels have less/no ethanol whereas all regular unleaded fuels have it. Ethanol damages alloy carb parts and alloy fuel tanks etc. Also it deteriorates more quickly over time so our cars left over the winter with little or no use are better off with super unleaded in the tank and maybe some fuel conditioner in there too. Also, it is better to leave the fuel tank full for storage since this reduces the danger of condensation on the interior walls of the tank.
