My 05 V8 says 365 mile range (roughly) when I fill it up. I get about 16-19mpg (19mpg is 95% highway) keeping it below 70mph. The post that says 75-85mph is the sweet spot....ridiculous. I would say its around 40-45mph in 5th gear. which would get you 23+mpg....but that is too slow for highway driving in California. Tons of 65mph and 70mph signs to adhere to. Anything below 15mpg (hand calculated) with a light foot on mostly flat ground......something is not running right (efficiently)