Fwiw I don't think that is an issue to worry about. Back in March I drove to Miami and back in my MR Ecoboost to pick up several thousand pounds of Venetian brick veneer and carefully measured MPG both down and back with cruise control set. Zero difference at least at cruising speeds.You might want to calculate the weight before going this route, depending on both how heavy your build is and your combination of wheelbase / body style / roof height. LINE-X weighs around .7 pounds per square foot so it probably wouldn't be that bad, but some builds are cutting it close with a full tank, water topped off, and all seats occupied. Just a thought.