I just towed a 25' camper 3 1/2 hrs mostly highway 2 days ago with a 2000 ext cab 4X4 3.9 auto 3.92 gears 193K miles. That being said its not something I plan to do often. Would have rather had a V8. 65-70 was achieved without OD, not going to get moving quickly, but will maintain except for big hills. I was at approx 5000 lbs trailer weight and got approx 9 mpg. Like I said, I wouldn't recommend it over the long haul without a V8 and proper gearing.