I have a friend who tows his 2700 pound GT2 car won an aluminum trailer behind his VW Toureg. Seems happy with it.
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The Touareg is rated at a nice 7700 lbs. But unfortunately it doesn't get mileage any better than many real tow vehicles which was a requirement for the OP. Of course, it blows away the mileage of my 8.1L gas Suburban!