I'm trying to squeeze out every mile per gallon out of my 98 nascar f150. I have a new set of firestone destination LE's on it. Love the tires. The door jamb says to set the front tires to 26psi, and the rears to 29psi. The tire itself says the maximum inflation is 44psi. I have been running the stock specs, I have a 400 pound load of sandbags in the bed all winter. Think I could go up a few pounds (like 5psi), in all the tires and not worry about anything? I wonder why ford suggested such a low tire pressure.