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Hey Wil. Simply put it really comes down to the overall package for Larry and I. Modern OEM fuel injection is a large part of our mileage. His with the 8.1 and mine with the 5.3. Then gearing that is well matched to the tire size is very helpful to the mileage on and off road. We both run 315/75-16 tires. He is running 4.56's and I'm running 4.10's. Mine is a little undergeared for my tire size, but it is better than having 3.73's or less. Crappy gearing with large tires it probably one of the biggest ways to kill the mileage.

Once we are off pavement we don't drive with any overall strategy for fuel mileage. Other than staying out of low range until needed. Due to the wide difference between Larry's truck and mine we do drive a little differently though off road. In the desert where we aren't crawling, I may or not be 4hi and leave the shifter in od for the auto. We may be traveling too slow so it doesn't always get into od though. In the same situation Larry is more apt to leave the 5 speed in 3rd and creep along lugging the 8.1 to the point the engine is running slow enough you'd think you can hear each cylinder fire separately. despite the difference in how we drive them the results are very similar. Hell, off road it's no different than our buddy's mileage in his Dodge with a 24v Cummins driving with us.

Planning is key on the desert trips though. With my 5.3 and the weight and drag of the camper my overall average is around 12-13 mpg on the pavement. With the 31 gallon tank it gives me right at 400 miles per tank range. Off road I've seen around 10 in the desert so it's a little over 300 miles on a full tank. The fuel cans are extra insurance as we both try to carry two 5 gallon cans which for me is an added 100 miles of range.

I'm a nerd when it comes to tracking mileage though. I've got an app on my phone I plug in every tank into.

Weight sure makes a difference, but both of us having campers ups the poundage for sure. Larry's weighs in at 8,000 pounds loaded for a week and mine is right at 6,300 and growing. So being heavy and shaped like a barn door is not helping. My first desert trip without the camper had better overall trip average to this last years trip for sure.

Tire pressure is a factor for mileage on road, but off road that goes out the window. We dump the tire pressure for comfort. We did about 80 miles of the Mojave road on dirt and close to another 100 getting to and getting out of the Tuweep area of the North rim of the Grand Canyon. Washboard dirt roads and street air pressure don't mix. So we sacrificed some economy for comfort. But I don't think the difference would be measured as very much anyway.

Mountain trips local to us are a different game compared to the long distance desert runs. We tend to leave the fuel cans at home. Tanks are full when we leave home and then we top off near the trailhead. Typically we can wheel all weekend in low range, get back to pavement and drive home without stopping for fuel. We also aren't loaded to the same extent since we typically only go out for a weekend run to the mountains.