My Rpm with the 35" tires I had ( second set after truck was new) was 2200 rpm at 65mph

When I switched to the BFG AT 37" tires my RPM dropped to 1900rpm and my fuel economy stayed exactly the same. Seems that the additional weight and inertia was a wash for the drop in RPM. I had the Odometer and speedometer reprogrammed to the tire size in each case. It was confirmed with my GPS

Staying with the same diameter but going way up in width and weight with the toys MT's My MPG dropped big time! The drop in RPM could not overcome the massive size and rolling resistance of those huge Toyo MT's

So I need to head back to the lighter D rated tires like those I have mentioned. The least aggressive is typically the least rolling resistance however that is not always the case because of the rubber compounds and if they are snow rated. Snow rated tires usually have the highest rolling resistance because the compounds are softer.

Visually the geolander is the smoothest tread pattern, hence the lowest rolling resistance. Don't know much about Yokohama beyond this.

The coopers are 400 bucks a set cheaper then the Nitto's. However you can suck up 400 bucks in fuel pretty quick so that alone is not the decision maker. I do like the reviews and performance of the coopers. Although on the cummins diesel forum there seems to be a lot of folks that really like the Nitto Terra Grapplers too.

One other thought, the Nitto's are 36 ish in height not actually the 37 marked. The others are all 36.8 to 37" tall. Maybe the slightly shorter 36" tire makes the best sense?

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