RE: Towing efficiency as a ratio of tow rating to actual load
I don't know the formulae, but here is what I just got. Round trip from near Tucson, AZ to Seattle and back. I pulled my Nash 22H pretty well loaded up. It weighs about 5500. I got 11.9 mpg. That was with 5300 miles, about 4300 towing and 1000 bumming around. I drove north thru Arizona, Utah, Idaho, Oregon into Washington. Lots of hills and I avoided freeways often. I usually had a small tail wind. I drove back thru California, usually into the wind and on the freeways.
My 5.4 Ford has 300 hp and 365 fp of torque and is rated to tow 9000 lbs, so the tow very easy for me.
RE: Can I tow a 2008 Cougar Lite 29 foot trailer
I'd be scared to put those two together. I towed my Nash 22H with an '01 Expy for quite well, but it was only 24', only about 4300 dry, and 5500 loaded up. My Expy had the 2 valve 5.4, (260 hp) with 3.55 gears. The engine was OK for the load.
But at 29', your 119" wheelbase is too short.
