Gunny,
Despite a number of other people discussing their rig configurations and mileage impacts, my prior reply to you was deleted because "The folks who have been posting in the Thread 'ECO Hubs who needs 3:07 Gears?' have requested that you start your own thread about your current trip."
Not sure I understand why my mileage data and user experience from the hub delete isn't relevant to this conversation. It's a 2000 M1088, ~26k #, 8' wide, 12' 5" high, ~23' box on back, 3.07's with the Eco Hubs, 330hp 3126.
I will share again that I was on I-84 and I-15 from Portland to Spanish Fork, and then Rt 6 over to Wellington (9k Soldier Pass). For this leg I averaged about 8.5 MPG fully loaded and keeping it under 65 (or trying). Uphill travel I was sympathetic and slowed, but was never as slow as the big rigs. Once I hit the dirt, mileage dropped into the low 7's typically, with some smaller fills of high 6's. I had one outlier of ~55 miles on ~10.5 gallons, but that was on a bunch of uphill, rough dirt/gravel road at higher altitude (up to 7,900'). Our return route was the same from Spanish Fork back to Portland, and I still need to fill up following our last leg to home, but if I had to guess, I'd say we averaged just over 8 MPG for the entire trip, with a high of 8.9 MPG on two highway tanks.
One destination later in the trip, I had an extremely sandy stretch for about an hour each way. The truck was lighter than the start, but not by much (just food and water depletion), and it was able to dispense with the terrain without issue. This was also a ~5 MPG fill as well. There was a 0.3 mile stretch where the soft, loose sand was as deep as the sidewalls. My wife caught our departure on video:
You can see the sand billowing away from the tires. It was extremely soft and fairly deep. Truck did fine without the reduction set.
I am happy to support Mike and share any other info about my personal experience with the Eco Hubs. They are well made and have been a great mod for my application. If I were still considering them, this is exactly the info I'd be looking for. Ask away with any other question or send me a PM if you'd prefer.
Mods - Respectfully, if this is still considered inappropriate, please let me know what I need to filter out to share the experience instead of deleting it.
Chris