We have a Jetta TDI, 5 speed manual. We had a Hidden Hitch installed and bought a light aluminum trailer.
She hauled the Harley to Florida twice, from SW PA through the mountains of WV and VA. Even hauling over 1000 pounds plus all ourselves and luggage for a 2 week stay, we got 38MPG.
I have always been in the habit of resetting the trip odometer when I fill up, and check the mileage with each tank. With 80% city driving, I average 43 MPG, even with 8 full years and 170k miles on her.
One word of warning with the VW though, they are notorious for wiring issues. I've had the harness in the drivers side door replaced once already due to the opening/closing of the door pinching and breaking the wires. Likely will have to have it done again.