Have posted before on this but thought I would give an update as this was my longest and heaviest tow to date. I have a 3500 pound dry weight toy hauler loaded with about 1000 pounds of stuff, including a Harley dyna super glide. Trip was from central NJ to the Shenandoah Valley in Virginia. I have a 2012 4dr sport with manual trans and max tow package (3.73 rear). I also have dual axle brakes on the trailer, a brake controller and friction sway control. Except for the significant need for power, the trailer towed like a dream. No wandering, no sway. I kept it around 60-65 and felt like I had very good control. It is only possible to go about 73mph. Just not enough power to go any faster. My mpg was 11.5. What I have found in previous trips is that 60mph gives 12mpg and 70mph gives about 11mpg. It towed great, but I don't think I would want to do it with the old engine or with lower numbered gears. Also, I have not noticed much difference compared to towing the trailer empty vs towing it loaded. I guess the box towing a bigger box just has some aero limitations, regardless of weight.