Unfortunately some states have posted speed limits of 70 and its hard to be an obstruction in traffic on a small interstate (2 lanes both ways). I used to curse the 55mph speed limit on the interstate near richmond, but now I love it

A hybrid is a good choice, just try to get yourself behind someone big and draft

*shameful* I was behind this huge honkin Racing Truck, Was wider than a normal tractor trailer, but it was barrelling down the road at 80 mph, I followed it for nearly 70miles averaging 48mpg. It was amazing */shameful*

Oh and the time to buy a hybrid was about 6 months ago