When I get on the interstate anymore I fall in behind a truck. Keeps my pace fairly steady and I don't really feel like having to do the speed limit anymore now that I live somewhere that the limit is faster than I like to drive. Both aspects help with gas mileage. Though I do try to stay a decent distance back and also run a CB so I can talk to them.
What I don't like is when they have to be within a couple pick-up lengths off my bumper, after catching up to me, and then won't pass, even after I pull over to let them by.
Funny how a phone chat with a sheriff's dispatcher near a fairly populated area can take care of that.