I no longer own a fiberglass camper, got a Geo Pro 19BH but I stuck around anyway
The camper is 3,100lbs.
I was towing it with a Nissan Quest (6 cylinder) rated to pull 3,500lbs and at speeds of about 60mph I would average 11mpg on relatively flat terrain.
I just traded in the mini van for a GMC canyon SLT with the 2.8-liter Duramax
I bought the truck used for 28K and it had 45,000 miles on it. It has a built in brake controller and also has an exhaust brake.
Fuel economy towing at 60mph with the exact same trailer on the exact same trip was 15.5mpg.
The exhaust brake feels like the truck is downshifting when it kicks in but it is very smooth. The truck is extremely quiet even compared to the minivan and if I'm not towing on that same drive I'll get about 36mpg.
It rides like a big truck and it sounds like a big truck when you start it up. I'm very happy with it and I like the interior much better than a Ranger but it is also a lot more money!
Only problem is now that we have a vehicle that can pull 7,700lbs the wife wants a bigger camper