I recommend 5k miles. Fluids are so cheap. 12 quarts of mobile 1 is $50? At Walmart. The filters are around $10-15.00 or buy 2 of the 5 quart deals at advance or auto zone that come with filter for around $35, and grab another 5 qt jug at Walmart for $28ish bucks. These engines rely on fluids being clean to operate properly, amongst so.e other things in your control....