I'm towing an E30 race car on an 18' open trailer. Trailer's got electric brakes, and I'm using a Tekonsha P3 brake controller. All in with my spares I think I'm towing around 4500#. I get about 20 MPG towing, and easily do the speed limit anywhere. Heck, it doesn't even gear down for most hills. It feels really stable with the trailer behind, no worries at all. Go for it!

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#55 Pro3
91 318is
10 X5 35d