This was my load for Big Bend, trailer (12'x6'7" with folding gate) is roughly 1,300lbs, three bikes at roughly 950lbs. Another 150lbs in gear/fuel/chocks on the trailer and three grown men plus all of our riding gear and bags for five days (lets call that another 750lbs) for a total of just over 3,000lbs. The truck is lifted 2.5-3" on 285/70's with stock gearing, traveling on relatively flat terrain under 1000ft ASL at 70mph we were getting 10-11mpg, I thought that was just ok but pretty much as to be expected. As we reached west Texas and started climbing in altitude over and through the mountains and passes we dropped significantly to an average of 8-9mpg and we saw as low as 7.8mpg average on one tank coming back.
I am glad that I am adding the LRA 33gal aux fuel tank (it would have already been installed if not for this current state of affairs) and it would have helped quite a bit on this trip to lessen the fuel stops and keep the higher dollar west Texas fuel prices to a minimum. That said, I don't foresee myself doing any long distance hauling with it in the future after these results, those numbers are pretty bad IMHO. Granted these trips aren't the norm and when using the currently cheap 87 RUG you can absorb the bad mileage, but when covering 1,400 miles it certainly has an impact. My around town average is 15-15.5mpg and on the highway I usually see 16-17.5mpg, so getting 60% less on one tank on the way home was eye opening. I've towed a ton over the years with 3/4-ton and 1-ton diesels so I am aware of what to expect, but for some reason I had higher hopes considering that this load was only half of what the truck is rated for.
With all of that said, I have to admit that I was impressed with how effortlessly the GX towed this load. There was no swaying, hopping, pushing, or skittering and at times I forgot the load was even back there. It was noticeable when climbing some of the 10+ degree grades but that is to be expected. The GX is a night and day improvement over the 5th Gen in this category and for that I am grateful. One perk was that we were all much more comfortable in the GX on this trip when compared to my buddies RAM 2500 diesel 4x4 we usually travel in. The quieter cabin certainly helped on the stress levels and allowed for us to more easily carry on conversations while traveling, every single one of us mentioned this along the way.
I am sure that we could have improved those fuel economy numbers had we slowed down to 60-65mph but on the interstate (where you get run over doing anything less than the speed limit of 75mph) and when covering 9-9.5 hours one direction it simply wasn't an option given our time frame. And quite honestly, the 1-2mpg improvement we might have seen by slowing down simply wouldn't be worth the time added to the trip. Overall, it wasn't a bad trip with this load, just crappier fuel economy than expected, I will be installing the RedArc electronic brake controller in the future should we do anymore trips towing with it.