You have provided some good data points here. One is the fuel comment. I buy mine at just a few stations here in DFW and a couple on the road to the ranch in NM. YES there is a difference in fuel and it will impact mileage. The other is TP--run all of mine at 70 Cold (adjusted just last week for cooler temps had to add 4 lbs) when running empty and yes they go up a few lbs when hot but no issues even if they are at 80 psi cold and go to 84 or more they are designed to do that.I went from a 295/55/20 to the 305/55/20. My mileage decreased before the tire change. The tuning service I use wanted to know what the difference between the Speedometer and gps at those speeds. I understand the dic isn’t accurate it has just been crazy to see it drop over those when it stayed constantly at 18.5 for so long. Sounds like part of it could be due to the lower cetane in diesel now. I also found all four tires at different pressures today ranging from 62 to 80 psi.