That's very interesting... I run premium 93 from Costco and average about the same gas mileage. Typically around 15-16 MPG. I typically let my truck warm up for 15-20 mins in the morning, or else it would be a lot higher. My first couple weeks driving my raptor I average around 17.5 MPG, and that was during the middle of August. I drive with cruise control mostly because all my driving consist of highway miles. At least where I live it doesn't get much above freezing.