What kind of vehicle do you have:
2007 Dodge Ram Megacab 5.9L Cummins Diesel 2WD. Trailer is a 20’ enclosed trailer, tandem 7000# axles. Truck, trailer, car, tires/wheels, spares puts on the road at close to 15,800lbs. Mods to truck: AEM intake and intake horn, 4" exhaust cat-back, Edge Juice w/Attitude Tuner
What do you Like about it:
Fuel economy towing (sane towing speeds ~70MPH) 14.6 MPG. (less sane ~80MPH, it drops to closer to 11.5). Cummins reliability, huge cab, lots of room for people and gear. Solid in the wet or dry towing.
3/4 ton suspension can handle the heavy trailer weights without a weight distribution hitch.
What do you dislike about it:
Transmission. This is the weak link on Dodge trucks. I’m getting close to 80K miles on the clock and feel a new tranny in the near future. That said, once you replace the tranny (at least with a good one), these drivetrains are rock solid and easily 500K mile motors. Interior (somewhat), the new Ford cabs are amazing inside, the Dodge cab has less frills. Functional, but not as nice as the Fords.
What would you buy to replace it: Another Dodge Ram Diesel, just with 4WD. Maybe newer.
This all said, I am big fan of diesel power for towing. Aside from the race trailer, we also tow our 30’ travel trailer RV. While towing MPG of 14.6 vs 11 may not seem like much, it is almost a 33% increase in fuel economy. I also run the truck on bio-diesel when ever I can. I used to have a supplier here in S FL, but they closed.
Keep in mind there is a huge difference in open vs closed trailers. Weight has very little impact on fuel economy for me. It’s all wind drag. The faster I go, the lower the MPG’s drop. I can pull my trailer empty (1380lbs), full or my RV and get just about the same fuel economy. It’s only really effected by speed.