Took me a while to find this thread again. "MPG" is too short to search for. Anyway - I just wanted to update this thread. I will be taking off on a hunting trip next week and placing about 3500 miles on the truck, been very "scientific" about which gas I am going to use. Here is what I did: I used 93 for the first 13xx miles. Average about 17.7 MPG (I don't go nuts on the S+ mode) Switched to 89 from 13xx-3000 miles. Averaged 16.75 MPG Just switched back to 93 with about 7gal of 89 still in the tank. I am up over 18MPG. I also notice a bit more 'pep' when driving. Given the amount of highway driving I will be doing, I am all over the 93 (or 91 if it is all I can find) for the trek. So IMO higher octane is what these engines like and will prefer.