I just towed about 6k lbs with my N55 X5. I was burning a quarter tank of fuel for every 50-60 miles. That equates to 11-12 mpg. I was cruising about 75 for a period of time with the trailer. However when I slowed down I could tell the tank of gas was getting me farther. I would say it towed fine, however braking was tough.
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