MFL wrote:
I would rather use OEM tailgate, that is more secure when parked in CG. I don't think you would notice any mileage difference, but maybe a little less turbulence. I would just make sure to have some good flaps on the truck, to deflect rocks/mud. I would not bother with diamond plate either. If you tow off hi-way, on gravel etc, your experience may be different than mine.
Jerry
People worry more about mudflaps when they go up to Alaska since many of the roads up there are gravel. The only problem I've ever had with a rock is one that came flying off a rock truck going the other way. On paved roads it's not that much of an issue tho I saw some posts about CA roads being a problem.