Originally Posted by sokhapkin
It's a myth that truck shell improves MPG. Usually MPG drops a little because of added weight
I agree. The caps are big and heavy and it is not only the weight
, but the volume of air they displace and push around, increasing the drag.
A bed cover (tonneau), on the other hand, is widely considered a benefit, based on my quick google search. The change may be small, 20 mpg increased to 21 mpg (5%). I made myself a cover shortly after I got the truck and I can see the benefit. The cover is light weight
and easily removed when I have to put the hitch in the bed. The weight of the hitch and the cover are pretty close.