An old Mantis (two cycle mini tiller) would not run right. I took it for repair and was told the ethanol in the gas ruined parts in the carburetor. They rebuilt it and told me to use an additive going forward. There was also an article in the Lauren Fix column in my newspaper recommending a specific (and different) additive to prevent auto damage from the ethanol. Auto parts stores now have several different additives for this purpose. The questions. Is 10% ethanol bad for engines? Is it bad for all engines? Which, if any, of the available additives do any good?