My driving is pretty much strictly scenario #2.

City miles are minimal, mostly highway, and no towing to speak of.

On the highway I can average 23 - 25 MPG in Canada, with occasional highs of 27. This with the tach at around 1900.

On the US interstate I-29 two weeks ago between here and Nebraska, I recorded a dismal 19 (75 MPH speed limit and a real strong south west wind). Tach on 2400 at 75 MPH, the old truck never knew what hit it. And me as a fuel mizer, I was ashamed of myself, at least somewhat, but shaved a couple hours off the time to get there.

Not so big of a rush to get home, even though took an hour or two longer, slow to 65 MPH and 24 MPG, tach still around 2000.

A previous post a few months back (may have been Moondoggie, not 100% sure) suggested before cleaning out the bank account to overhaul your truck to increase MPG, figure how much you could gain vs how much you spend.

I did the math at the time, and for me with the price of fuel as it was a couple months ago or more when that thread was up and running, if I spent 1000.00 on a 1 MPG increase, I could recover that amount in fuel savings in 140,000 miles. Well, not likely the truck will live that long, so for me, any opening of the engine, aftermarket exhaust, etc. would never pay for itself in fuel.

lots of mods "claim" higher mileage, but if you read this board, everyone who does any mods at all seems to gain weight on the right leg immediately, and I haven't heard of any drastic fuel mileage increases.

Maybe if my truck was newer, and had 300K ahead of it, there may be some benefit. But to me, I CAN drive 100KPH, and will, and will hopefully continue to be happy with the mileage.