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Question does a tonneau cover really help improve MPG's?
Reason is that I have one now but was thinking of keeping it off because I was going to get a Roll Bar in the bed. Thats if I can find one that fits my 2005 SD.
~Gage~
I think the tonneau cover MPG improvement idea has gone the way of the tail gate down or off for MPG idea..........it don't help. About the only way to impove MPG on the V-10 is with the control of the right foot pressure.
The right foot is the only major difference as jonrjen has already stated. You would be amazed how much better mileage you can get driving like an old lady. The tonneau cover might get you .009 MPG better, but you'll never notice it. I wouldn't buy a tonneau cover just for gas mileage, but they are handy. I love mine.
I beg to differ. I have one, and ride plenty w/o it, and plenty with it. I do get, at least, a minimum, of 1/2 mpg improvement (highway use) with the cover on. One should not purchase a cover with the sole intent of improving mileage. It will take some time to recoup the cost of the cover. Especially if bought from Agri, it ain't cheap.
I have religously run the numbers for the last 24,500 miles, of every tankful of gas I've burned since I bought the truck new. There is a slightly noticeable difference with the cover on.
As to the Myth-Busters. These guys are just like the Discovery Channel. Very interesting stuff, very compelling stories. But not always true, not always scientific, not always completely factual; and for sure possible, sometimes, slightly skewed. Just because these two guys made/make a living doing stunts for TV and movies, does not make them the be-all to end-all when it comes to many of the Myths they attempt to debunk.
I have a cab height topper/cap, and I always thought that with it on, I got 1/2 MPG or so better.
Then, last year, I took a 250+ mile trip without it, and found I STILL can get 16.2MPGs without it. I did have a lot of stuff in the bed, covered with a tarp though.
I think it all depends on the bed length, and cab length. In other words, a SB SC will have different results than a CC LB.
The air flowing over the cab and into the bed creates a "bubble" that the airflow then rides on top and over. There are more scientific experiments with diagrams and pressure charts on the net if you search for them.
There have been numerous studies done on the effect of tonneau covers and the effects on fuel mileage. The only "study" that I've seen where it didn't get better gas mileage was the Mythbuster's segment. It might make a difference what size your truck is, but everyone should be getting some gas saving advantage with a cover on.