At least on the northbound drive from Houston to Dallas, there are a large number of "rest stops" and "picnic stops" (the former having bathrooms and lame vending machines, where the latter is just parking plus a few benches). One could easily park a fuel truck at these stops. Once you get past the half-way point, the rest stops and such become fewer and further in between, but by then the traffic was moving efficiently, so there wouldn't be any such need.