2005 Mercury Racing Optimax 250XS Serial number 0T998654. I know my engine requires premium fuel (91 octane or higher), my question is, should I use 93 octane premium, or 91 octane ethanol free? The owners manual states not to use gasoline with more than 10% ethanol, and I am using Don's recommended cocktail of Quickleen and Quickcare.
Thank you.