I bought my Tradesman EcoD with 11,500 and it had the P rated stock tires. After towing my trailer a few thousand miles I decided I didn't like the tire squirm I was experiencing and decided to go to E rated Discoverer AT's. I had asked on this forum for advice in advance of the purchase and was told by one poster that I didn't need E rated tires because the P's were more than enough on a half ton truck. I disagree, I have run E's on virtually every truck I have owned and know they are extremely helpful when towing a 6000# travel trailer. The post that caught my eye though was the one telling me I was going to lose mpg with the E's. Much to my surprise I did lose between 2 & 4 mpg when not towing and I was sadly disappointed. My tow mileage however remained almost unchanged. After the last trip with the trailer I left the tires at 65 psi because of laziness, I generally run 45-50 psi unloaded. Much to my surprise my mpg is back up 3 mpg. Seems I need to run them a bit higher to retain my mpg. The only reason I rand 40-50 psi was ride quality. The truck obviously rides a bit stiffer at 65 psi than it does at 50 psi. I can live with that for 3 more mpg. Just thought this was interesting.