I am going to be moving at the end of July and I don't want to rent some POS Uhaul Truck and have to pay fuel in two vehicles.

Does anyone know any ideas to rent an enclosed trailer at least 16' so I can save fuel and not be driving some 20yr old POS gasser moving truck that is likely to break down

probably not what you want to hear but uhaul does rent trailers.

but the largest is 6x12

rcs or sunbelt dont know if you have those

Check your local tool rental places - there are at least 3 here that have enclosed trailers...

If your'e looking to rent one way it will be expensive,and tough to find except for uhaul.even then uhaul wants double one way over bringing it back where you got it. my nephew in the military,decided to rent it at his base drive it home empty,and drive it back. saved half over renting at home and moving to base.

Been a while, but I couldn't find one way trailer rentals for cargo trailers or big utility trailers, 'cept for the UHaul junk.
Twice now, I've bought a trailer, moved with it and then sold it at the new location. 1st time, I got the trailer sold before my CC bill even came due! 2nd time, I bought a cargo trailer, used it for all my tools (mini shop, no garage), moved twice with it and sold it a year and a half later for $400 less than I paid for it.
Look into that.

Why not buy one, then sell it? They hold their value pretty well.

I am only moving 100 miles so I don't think it would be worth it

Most tool rental and trailer shops around here rent several sizes of open utility/equip trailers. A couple rent smaller enclosed i.e. 5x10 or 6x12. Hate to say it, but Uhaul is probably your best bet for trailer rental on enclosed. you could go open and spend a little on 2x4's and a good tarp to build side rails and cover it. For a 100mi trip if weather is forecast half decent you might have better selection going that way.

if you are running 100 miles, who not rent a flatbed trailer, and tarp it? I moved ~100 and that's (2 axle care trailer) what we (family) did last sept.

Check out local equipment rental places, and some car dealers. There are some both locally in my area who have 16' cargo trailers. Don't know of anyone with bigger ones than that.