Add the fairings or not???

The ones on the sides of the cab are called cab extenders.

The big one on top is called an air dam.

 

I don't know what your total cost will be. But you should go up in mpg, depending on how you drive, to 6.5 or 7ish.

Compared to 5 mpg, at a 100K miles a year, that's $15K in fuel you'll save.

 

How big is the gap from the sleeper to the trailer?

 

What trailer are u pulling?

 

If you are pulling a van trailer the air dam is the most important.

I thought most trucks already have the cab extenders behind the sleeper.

If you work on your own truck you probably won't like the fairings... I don't think you can get under the truck unless you jack it up or remove something.

Maybe there is something else going on with your truck that you only are getting 5 miles to the gallon?

 

If you are a flatbedder forget it.

Its kind of nice to be a midroof, you can get under certain bridges say 12 foot 3 inches with your stack at 12 foot two. IF you were a flatbedder....

If you were in Nogales all that empty space above your midroof sleeper becomes a hiding place for illegals. They will absolutely go up there and snuggle hoping to get past the Border patrol checkpoints.

5 miles to the gallon is a problem with something else. My 1994 midroof volvo got 6 even most of the time with a covered wagon.

 

How heavy are you usually pulling? 5mpg is horrible for a D13.