I can't imagine there would be much lose in MGP due to air flow. There’s a lot of other things the air would go through first. Track bar drag link, axle, I don’t know maybe. I would link that weight would be a bigger factor. The more we bolt on the heavier our rigs get, the worst MPG.
I recently picked up a t-case and gas tank skid from the pick apart. For a grand total of $16 out the door.
I really like the idea of a gas tank skid cause its low and in the rear just waiting for the stuck as I drop down a rise.