i have a grubee 66cc and i have read and talked to some dealers about the correct mix ratio, the factory instructions say 4 oz. per gallon but the people i talked to say anywhere from 7 to 8 oz. per gallon. right now i'm using 8oz per gallon to be safe, this way i know that none of the internal parts are being damaged due to lack of oil. i've also been told that more oil increases power, not sure if thats true but i'd like to know what fuel mix gets the optimum performance and still provides proper lubrication? also what problems can be caused by using too much oil i know that the plug will foul out quicker but what other issues will it cause?