[elhigh]

There's a bit heading south on I-75 in Tennessee, as you're approaching Caryville / Jacksboro, where you can turn the engine off and go for about 2.5 - 3 miles. If your aero is right and you're not dragging any brakes, you can pick up quite a bit of speed. My truck with no aero mods will slowly climb up to about 70mph and hold there.

I don't make that run very often, though. I'm usually lucky to get more than a quarter-mile of silent gliding, but there's a run heading northbound on I-75 where I can usually come close to a full mile.