Any truth to mpg claims with bed covers?

[ksadz]

I'm not getting one for that purpose, but some of these manufacturers are claiming up to a 10% mileage improvement. With fuel prices like they are, I'll take anything I can get. What are your experiences?

 

[jponder]

There was a post about some drag test done on trucks.



Tonneau cover was better. here is the rank as I remember them



worst

TailGate off

tailgate up

tailgate down

Tonneau cover

Bed high cap that swooped down in back



It was a surprise to see that tailgate up was less drag than it being off.



I cant imagine you would see a 10% increase, but maybe . 1 MPG

 

[Hammer]

You of course realize that these trucks were designed for running with the tailgates up and still get the fuel mileage you seek,without any cover over the bed... ... ... . Andy

 

[RRoton]

The higher the speed, the more difference a bed cover will make.

But, for 10%, you would PROBALLY have to be going 100MPH.

Just my opinion, no facts to back it up.

 

[jponder]

I was thinking the same thing RR, Back when i used to make mileage runs, Meaning I would drive 55 with a throttle cable and roll with the hills, I thought I should maybe make some funky looking cap that would be cab high and feather to the end of the lowered Tail gate.



It dawned on me that it might help for fast speeds but I probably would get more mileage by just slowing to 45!

 

[CRuth]

I remember reading about some wind tunnel tests once. They found it was better to leave the tailgate up than down. Don't know what tonneau cover would do.



Craig

 

[JWChessell]

In July 2003 I purchased a CTD 3500 QC SRW, and immediately put a shell on it, so don't have any figures for fuel consumption with/without the shell for my Cummins 3500. HOWEVER, from 1989 to 2003 I owned an 1981 Chev 1-ton pickup, 4-dr crew-cab 8' bed, DRW, 454 cu in GAS, Turbo 400 auto trans, 4. 10 rear end. For the 1st year after I bought it, there was no shell or bed cover, just the open cab. I kept several types of records, including gallons-per-fuel purchase; daily mileage on different errands (for taxes), avg speed on long trips, -- more than 200 miles one way -- psi tire pressure, and so forth. During that 1st year of open-bed driving with the bed either empty or lightly loaded, I averaged 10 mpg with the tailgate up, and 11 mpg with the tail gate down -- a 10 per cent difference. I know that does not coincide with the "wind tunnel tests" that people speak of, but I know my records are accurate. 10 mpg with the tailgate up, and 11 mpg with the tailgate down -- a 10% increase in fuel mileage, or a 10% decrease in fuel consumption, depending on how you look at it.

 

[Spooled-up]

I have noticed maybe a . 5mpg difference with my tonneau cover on. My milage varies by that much sometimes though. But on average, the trend is that I get a little better mileage with it on. I usually remove it for the winter to keep it in good shape. Too many variables to tell for sure if it makes a difference.

 

[Slick]

I too read an article a while back, not sure if it was the same one as CRuth, but at any rate there are several factors that influence the mpg efficiency concerning the tailgate up, down or off. However, make and speeds have a definite impact on these stats too. Some makes at certain speeds had different "drag" stats than other makes at the same speeds with tailgates up or down. In most cases tailgates down or off had worse "drag" than tailgates up. The article also mention that bed covers and toppers also reduce "drag". Testing was done in a wind tunnel. At any rate I would agree that any bed cover would help some. My tcw.

 

[sewman]

I past a Ram on eway during the rain & looked over @ the rain going over the cab & over the top of the tailgate & it looked like they say designed in a wind tunnel. It didn't drop (the airflow) I suppose the older trucks could be different these?

Bob

 

[Jeremiah]

Tonneau wins

The tonneau wins the mpg contest, but not by much compared to a tailgate in the up position. I have the Access roll-up, which is guaranteed for the life of the truck driven by the original purchaser. Can't get any better than that.

 

[americana]

for what it's worth. i get 0. 5%=1mpg better. i've got a gem top fiberglass bed cover.

 

[RRuggles]

RE the wind tunnel tests: it was found with the tailgate up, that a sort of air bubble formed in the box deflecting the airflow up and over, improving mileage, but it was also said that probably the difference would be so small that ,with the precision of the available numbers, it would be barely noticeable.

 

[yyzski]

I found the difference to be more noticeable on a gas powered truck than on a Cummins.



When I installed a soft tonneau on my '96 with 5. 2/auto, mileage increased consistently by 2-3mpg highway (I tend to drive between 75-85mph most of the time). Looking in the rearview mirror you can see the cover distort from the difference in air pressure (pressed in towards the back of the bed, 'bubbling up' near the front - this may also have some effect on smoothing out the airflow more than with a hard tonneau.



On my '02 Cummins which is equipped with exactly the same tonneau I've not yet noticed a significant difference though I will need to run through many more tankfuls still... ...