I drove a 1981 VW Rabbit with an anemic 48 HP diesel. Like all my other diesels I put a second tank in it--this one took the place of the spare tire and doubled the fuel capacity to 20 gal with a corresponding gain in weight
Believe it or not I used it as a tow vehicle. I towed an old steel motorcycle trailer turned into a snow machine hauler. I'll guess it weighted 1100 lbs or more.
I don't recall my fuel economy. The car was rated 41 mpg on the highway but I drove it flat out at times and drive fast downhill to help make it up the next without losing too much speed. I rarely got more than 38 mpg. Around town I commonly got 34-36. Driving it hard, low 30's.
A few interesting facts.
It was surprisingly stable towing, particularly on ice. I had snow tires
on the front and was able to avoid a 25 car pileup on the interstate during one ice storm--perhaps it was the tires
, but I did lose traction and was able to regain it.
Fuel economy whilst towing. I don't recall exactly. Probably a relatively small hit, but I did struggle going up hill and slowed down traffic pulling over often. It was about 25-29 mpg pure estimate because it was many years ago.
Pick was decent and the manual transmission was trouble free. I never changed the clutch while I had it.
I rust proofed it when I bought it and it had everything mechanical broken when I sold it (my brother beat on it and gave it no msintenance). and no rust. He reported getting the best ever fuel economy 42. And also trailered with a much heavier trailer at slow speeds in the interstate.
I just wanted people to know that you can tow with a small diesel and if you get a speeding ticket while towing the judge will throw it out.
The combination of a front wheel drive and manual is not a bad one, and in a diesel you will get the best possible fuel economy towing. I would not use the highest gears, drive fast, or an automatic.
Probably the cheapest tow rig for fuel economy would be a VW 4 cyl diesel and one of the lighter egg campers.
If the Tiguan had a diesel I'd consider it.