Towing a 21 foot 4500lb travel trailer at 62mph I am happy with 12.5 to 13 MPG. HOWEVER, I always pull into a strong headwind so it usually comes out to 10.5 to 11.5 MPG. If I travel south, wind is out of the south. If I travel north, wind is out of the north. I use 91-93 octane.