I have been away for a few days to a wedding in Kansas. I filled up my car yesterday there and drove all the way back to Illinois and got 385 miles out of the tank in my 1998 Ford Mustang GT before I had to fill it up again to make it the rest of the way home. There was some speeding involved. The best I ever got prior to that was 350 miles out of a tank which was all highway miles like the Kansas trip. I am curious why it improved so much. I wasn't driving slow. I did change out my Mobil 1 EP 5W-30 SL to the SM version before I left and ran Shell premium gas. Anyway, I just thought I would share.