As was stated, it goes to what your machine will tolerate. I've owned some Honda products that I swear would run on 3.2 Beer! My higher mileage Dakota, I can tell within 50-100 miles from filling an empty tank what gas is in there. Arco is NEVER, causes a noticable surge! Shell is slightly better The 3.9 prefers Chevron... Just how this vehicle runs and what it prefers...for 5-7 cents/gal (a BUCK to a $1.50 on a fill) I don't sweat it