Thread update now that I have some mileage figures for the new Ram 2500, with the 6.4 hemi.
I run 89 Octane in the summer as I get about 15% better mileage in hot weather. In cooler to cold weather, the 87 octane provides the same mileage as the 89 so I burn 87.
First Highway trip with the new truck, just for a run.
Did another run coming back from GP, with about 6500 Klms on the truck. Gas mileage is still improving.
Running with no trailer and scale weighed at 9,800 pounds, 2021 Ram with 6.4 and 3.73s, did a test run a few days ago. Reset the Evic each time we changed the primary direction of travel, heading east 40 mph wind out of the SW hitting on right rear corner, 19 mpg, turned south Wind now hitting right front corner and strong enough to move you around in the lane when it gusted, 14.8 mpg, then headed south SE, wind almost directly on the tailgate, 22 mpg.
So with 7000 klms on the truck, city, highway and about 3500 k hunting on real bad roads in 4x4 both low and high range the hand tabulated average all all fills currently sits at 16.35 mpg. Best mileage. 22.2 mpg over 500 km, worst 12.2, 400 klms with 350 in low range the other 50 in high range. That is a 60% improvement overall on my V10 under similar use parameters. Didn't really buy it for improved gas mileage but it certainly is a nice fringe benefit.