Based on the air tests I have seen the flow from over the truck clears the tailgate for the 5.5 and 6.5 beds. I have an 8ft bed so I wonder how well that air pocket works, have not yet seen the results from wind tunnel tests yet.

 

I'm still in the honeymoon stage of my truck getting over 550 miles on my 36 gallon tank (5.0 3.73s)... So maybe I gain or lose 5 miles per tank because I do or do not have a bed cover... Any gains or losses would seem negligible with our trucks...


My Peragon truck cover sure does look amazing and provides the exact utility I need. Love having a clean bed too... fuel economy performance was the second to last reason as to why I purchased my truck bed cover... For those that must know - the last reason was to shield my open bed from any chance of it raining glass bowls of lemon jello salad... I had a pretty big list of reasons - just to put into perspective where "fuel economy" fit in to it...

 

I'm still getting a cover, F the MPG's I want one to keep stuff in the back dry when out & about.

 

I have a topper on mine, and the MPG is not really any different than without it. It is true though, the shorter the box, the smaller difference made. The 8' beds capture enough air to cushion the flow over the truck, and that is where the largest gains happen. That air cushion reduces the drag behind the cab, so it only has to deal with the drag behind the tailgate, but drop or remove the tail gate and you double or triple the drag behind the cab. That holds true for any size box. I think with a topper though, the drag is slightly reduced by not having that air pocket and drag behind the cab, but there is a larger area behind the truck so there will be more drag, and I think that equalizes the drag coefficient. That's probably why I have not seen any change in MPG, even with the added weight of the topper.


When I had a Tonue, I saw no gains or losses either, but at least the bed was dry.

 

I would imagine if a cover added any significant mpg gains the truck manufacturers would include cheap ones on all the trucks so that they would be standard equipment and would improve numbers for cafe testing.

 

The Mythbusters did an episode on this and showed leaving the tailgate down actually decreased MPG. Their discoveries seemed logical, although more extensive testing would be needed for an ultimate conclusion. They performed simulated wind tunnel testing (using a water tunnel) which showed having the tailgate up created vortices in the bed which may have decreased overall wind resistance.








As an engineer, I can understand why this works, but the actual MPG impact is probably minor compared to how you actually drive your truck.

 

You have to laugh at these advertisements that say "10% gas mileage improvements" maybe they meant 10 cents over the life of the vehicle.

 

15 F150 XLT SCREW 2.7 FX4 5.5 Box here and I drove the truck for about 4 months before getting a Backflip VP. I noticed 0% MPG increase after the install and it's been 6 months now since I've had it.

 

Any mpg gain is so insignificant, it is offset by the mpg loss due to the weight of the cover.
Add the expense of the cover, and you are in a huge loss.
Buy one for looks, convenience, and security.

 

Definitely some of the best advice I've read today!