I am now at 28,775 miles on my 2016 Limited short wheel base 4x4, 3.73 HD towing setup as well. My lifetime mileage is 15.46. This is all hand calculated and tracked via spreadsheet. The last two fill ups the on board computer has been roughly 6.5% and 5.5% off; on the optimistic side. Filled up this morning hand calculated was 17.98 and on board computer was 19.0, and the fill up before that was Friday and the on board computer said 17.7 and hand calculated it was 16.57. The last two fill ups have been at the same gas station at the same pump and have used mid octane gas. I purchased the expedition used in the 1st part of Nov and have put almost 16,000 miles on it. I have driven the same route to work with my 2014 Silverado crew cab 4x4, its lifetime mileage was 17.5, it was almost 19 before I put a heaver set of tires on it. But that thing shook like a junkie trying to kick heroin. For those of you who have been on any of the Chevy forums and read anything about the Chevy Shake, you will know what I am talking about. The dealer and I tried numerous things to fix it, new tires, new wheels, new drive shaft...nothing worked. You could drive the same road 10 times at the same speed, same direction and it might shake 7 out of 10 times...no rhyme or reason. Overall I like the way the Expedition drives, I am not too concerned about the gas mileage, its a big truck, and I knew what I was getting into when I choose a platform that was at the end of its life cycle.
