Ethanol in my truck bc its ethanol compliant with a stainless steel gas system. non-ethanol in the boats, 4 wheeler and lawn equipment. i wasn't caring too much until my boat started acting funny. if you are out in the boon docks and don't have much of a choice, keep some sta-bil ethanol treatment with you. it works great! Also, if i have to use e10 i get premium gas and add the ethanol treatment.