Caps/Toneau covers/Other truck bed covers - Fuel economy?

[Pookster]

What do you guys think about them They vary in price quite a bit, cap isnt really an option, but tossing it in there for comparison.

Fuel economy- Do these make a difference? I have heard they are good for a few MPG's. I tried driving with the tailgate down for a good stretch of road. Felt pretty good, seemed to have added 1 or so MPG.

My question is, with a tonnau cover, are you loosing your ability to strap stuff down? do they make ones with loops or strap hooks?

 

[cybrfire]

I made the tonneau cover on mine out of aluminum and hinged the last two foot or so like a trunk deck. I hardly ever haul anything so that wasn't a real concern. I feel that it did add a small amount to my gas mileage. Not much though. The biggest benefit was the lockable storage.