[aidenn0]

There are two numbers on the sticker for fuel efficiency. In-town and highway.

For in-town weight matters greatly (both because you essentially throw away energy every time you break, and because rolling-resistance matters more at low speed).

For highway, up until 2008 the maximum speed tested was 55, which disadvantages heavy-vehicles, as rolling resistance is a higher component of energy used at lower speeds (as a simple approximation, rolling-resistance is linear, and air-resistance is quadratic).

[sidewndr46]

The thread was specifically about a road trip. I can't imagine anyone taking a road trip entirely in town.

[bialpio]

Driving around Yosemite or Yellowstone is gonna be closer to in-town riding than to highway riding. I wouldn't be too surprised if time spent on driving at the destination was ~50% of my driving time at some road trips I took.

[aidenn0]

I've done road-trips entirely off of limited-access highways.