1999 2500 2wd 5.9l 24v, 410 rear end, 47re, Banks 4" exhaust. Took my first decent road trip since purchasing a couple months ago. 300+ miles each way towing 3500lb travel trailer, traveled from 1500 ft above sea level to over 7,000 with 6+% grades some several miles long. Averaged about 65 MPH entire trip, even up grades. Would love to hear your thoughts on these stats. MPG going up - just under 13; MPG unloaded- about 20.5, MPG coming back - about 14 (all hand calcs, not lie-o-meter). EGT averaged 800 - 1,000 (occasionally close to 1100 on steep grades - 500 - 600 on down grades). Now for the $64,000 question - since this seems to be a common point of discussion: Would you have made this trip with O/D on or off? Thanks for your insights.

Don't know much about your engine, but 20.5 mpg sounds pretty damn good to me; same with the loaded mpg.

From the sound of your route, I don't think I would have been in O/D for much of it. Zero % of the time when trailering (especially up- or downhill), and as "needed" when unloaded and on the flat.

Sounds like your rig is running very nicely.

You should post in the oil burner section. You'll get more feed back from those guys.

I wouldn't have used overdrive when towing especially over the grades but when empty I would've left OD on. Your pickup would have enough power especially with 4.10s to pull itself over most grades without downshifting.