Hey Richard, I looked up that Mopar warranty to see if I could get it for my 2004 Dakota with 143K miles and, what the heck!, they won't offer me one. It just isn't fair! 🤨
But I got around to calculating the mileage on our last trip. It wasn't too bad for a trip that required 2 3,000 foot climbs over two 7,500+ ft. mountain passes, with lots of intermediate climbs and descents. We got 12 mpg overall and made it back and forth on a single tank of gas. I think the "D" range tires likely added a couple tenths or so, but I could be wrong. We'll see when we drive down US 95 (not I-95) to AZ next month. [I suspect wind resistance is a much bigger factor in mileage than tire pressure.]