Right? That's why I started this thread...my '05 Suburban has always gotten really good mileage. I have checked dozens of times and my DIC and my manual calculations - no matter how I verify them - are always close enough the diff is negligible. The OD of the tires did not change, the stock size tires is a 265/70R16 and the new size I use is 245/75R16 - both of which have the same OD and are both factory/stock sizes on the 2wd half ton Suburban.

 

Last year we sold the '05 Suburban when it was about to hit 200K miles. It was a solid rig, and now my younger brother is using it to haul his family around on vacations to CA and back, etc. They love it.

We bought a 2011 Ford Expedition, 2wd 5.4L V8. Great vehicle, we love it. The Expedition does a better job towing than my Suburban did - mainly I believe due to the 6-speed transmission - but it does not get as good of mileage as the Suburban did. I attribute this to several things, one being that the Expedition has big heavy fancy wheels/tires from the factory. I am not disappointed in the mileage, just don't believe I'll ever get as good of mileage again as I got in the '05 Suburban. This Expedition has given me a best of 21 MPG when I was shooting for it. But pretty consistently will do 18-19 mpg on a trip, which I'm fine with. The interior seats and other appointments are so much better than our '05 Suburban (which we were happy with!) that I don't mind the trade-off in MPG's.