At highway speeds of up to 85 mph, averaging 73mph for the trip, my big 300M got 28.4 on the way out to Pittsburgh and 28.6 on the way back. I could only guess at what i would get if i kept it on cruise controll at 70mph, 30mpg ?? So far this stuff appears to be doing something as i have never seen these kind of numbers out of this car, especialy at these speeds. Anyone else out there trying this stuff? Results good or bad?
