I'm on my first long drive -- 420 miles in two days, first leg 240 miles, most of it on I-95. I experimented with drafting large trucks. When I was drafting, mostly at 65-70 and 30-40 yards back, I was using about 1 mile of range for each mile traveled. When not drafting I was consuming about 1.1 to 1.15 miles of range per mile. So at those speeds there seems to be about a minimum 10 percent gain in range. Not scientific for sure but clear results. I've never drafted before but with a sufficient margin it actually felt safer nestled in behind a large truck. From there one gets a great vantage point for all of the foolish driving going on.