Yes i have the mopar CAi.. the XDI is in my sig pic because i never got around to changing it... maybe ill do it tonight when im bored and noone is chattin

 

Lol that's BS. Just think about it logically.

Air flows over your truck at speed. Normally, it flows over your cab and since your cab abruptly ends, it dives down into your bed and is met with your tail gate, which offers resistance again.

With a tonneau cover, it drops down hit the tonneau and just slithers off the back.

I drove our truck one morning after we got the tonneau and the truck was covered in water drops because of the rain we got. After I reached my destination, all the water on the back half of the tonneau cover had flew off. This shows that after the air comes over the cab roof and drops down, it "falls" right before the tail gate, where it causes the most detriment to smooth airflow.

All I know is that the BEST mpg I ever saw with this truck before the tonneau was 21mpg doing 65mph. Afterwards I did 23.6mpg at 70mph...

 

yeah but i read somewhere that good designers make it so an air pocket forms inside the bed and creates like a low pressure bubble, positive air er something. kinda like if you have a bunch of leaves in the bed of your truck and start driving fast... the ones closet to the cab never fly out...

It could hurt your mileage. Myth busters did a show on having the tail gat down VS up. Having it down reduced the MPG by over 30 a tank which was over 1 MPG

also.. .a cover adds weight.. so driving around down your not going to get a big boost from aerodynamics, but youll be hauling extra weight..so youll lose gas... on the highway it makes more sense..

so you answer is.. ummm.... depends

 

LOL, your aerodynamic model of the truck is incorrect and everything else in your "logic" is incorrect because of it.

 

Uhh, that's fine. You believe what you want, I'll believe what I want, but if you're telling me air doesn't flow over a car then well...I dunno what to tell you.

Point is, I got better mileage after getting a tonneau. Do what you want, I don't care. I definitely don't change what I do just cause some idiot told me it was wrong.

 

We drive nearly 95% highway and have the 3.21 diff.

Before, getting the fuel saver on above 65mph was impossible. With the tonneau, I've had it kick in at as high as 80mph...

I definitely agree though, it'll do absolutely squat around town.

 

Before I installed my duals, I noted my MPG before the tornneau cover and after, it added 1-1 1/2 MPG highway after, city no change. About 5 years ago I drove my GT Vert stang 900 miles from Ft Stewart,Ga to Long Island New York with the top down the whole time, my MPG dropped from 25-26 to 22 MPG.When I drove that way 6 months later with the top up, the MPG was back up by 25-26. So atleast with my experience and vehicles, along with the barametric pressure and other unknown factors, it worked for me.Just kidding......................Kevin.