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
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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.