Why Thanks, Nick! Yup the Mark One calculator is best. In the old HAFC program we used a test nicknamed the Orange Test. You picked out a hiway route round trip of preferably at least 50 miles. Ideally w/ a gas station at the start next to the on ramp. You pick a pump, note just where you parked, fill up in a repeatable way (off at first click off of pump or whatever) reset trip odometer, get on to hiway get to a set speed like 60 or 65 mph, set cruise if avail or drive as steady as possible. Use a route as flat and straight as possible. Avoid accel or decel, just cruise steady for 25 miles, Ideally there is an off ramp w/ a quick turn around back on hiway, just get back to set speed and go back to start point at gas pump. Park at same pump in same position as first time fill back up to first click off. Get reciept then measure miles/gallons used. Comparing Oranges to Oranges. This way you test the Vehicle nothing else. You never take the same trip twice! Impossible to literally drive exactly the same way, but you try to get close for the most empirical results. This is ideal of course but there's a method to aim for. TracyG