The only fuel I buy is 87 non ethanol from the farm store. On all my small engines I put 6 ounces mmo in a 5 gal can then fill it for all engines except my car and truck. I never drain a tank or carb and have used gas that is 2 years old. I have a 2012 ford F150 with 5.0 and have found I average 3 mpg more on non ethanol 87 or 91. But I have better performance with the 87. Just my 02c