Optimal tire pressure for every vehicle will be different. Lots of variables come into play. The weight of the vehicle will be the biggest factor that affects tread wear at different PSI. ANY tire manufacturer will tell you to run the VEHICLE manufacturer's recommended pressure if you're running the stock sizes.
For instance, I run a 10 ply (Load Range E) on my Silverado 1500. The sidewall has 80 PSI max pressure. The door jam decal says 35 PSI. I've run them at 35, 40, 50 and 60 PSI. My mpg's did not change whatsoever with different inflations...but I get the most even tire wear and best ride at 40 PSI, so that's where I run them. I imagine running them less than 35 would begin to have some roll resistance...and build excess heat.
For instance, I run a 10 ply (Load Range E) on my Silverado 1500. The sidewall has 80 PSI max pressure. The door jam decal says 35 PSI. I've run them at 35, 40, 50 and 60 PSI. My mpg's did not change whatsoever with different inflations...but I get the most even tire wear and best ride at 40 PSI, so that's where I run them. I imagine running them less than 35 would begin to have some roll resistance...and build excess heat.