Don’t add weight. Increased vehicle weight decreases MPG. The harsh truth is simply this: Most of the upgrades we make to our pickups to improve their efficiency and performance in the work place hurt fuel economy.
Do keep tire pressures at vehicle recommended psi. Under-inflated tires hurt MPG. Under-inflated tires give fuel economy a hit; for every 1psi all four tires are under-inflated, there’s a .4-percent drop in fuel economy.