V8 with about 3500 miles on it, I have only had it on the highway once, when it was less then 500 miles (NEW) and it was a 160 mile trip one way---got it up to 15.5mpg. Will probably do better now. I have a trip to Atlanta coming up for the race there and will post my MPG from that trip. My around town stop/go driving, it stays around 13.7-14.2. All of this is as reported by the computers in the ST though, no actual calculations on my part...