The rear air suspension makes towing a pleasure. I've done several runs between FL & TX (1100 miles each way) with a 6k trailer. Drives so effortless I had to set the speed alarm to 85 when the wife drove a few legs, I looked at the speedo and saw over 90 mph several times. She's not a fast driver, just says the X has a reduced sense of speed (95mph feels like 75 mph).

Even towed my brothers 7500lb boat/trailer with 4 people/cargo, from northeast PA (mountains) to Toms River NJ. After letting my brother drive a few HWY miles, he said the X drives better then the 2011 F150 he uses to tow it.

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'03 X5 4.4 Sport, last of the M62s (8-03 build date)
I believe in deadication to craftmanship in a world of mediocrity!