I think the flatbeds are fine because I believe it is the sides of the bed that causes the turbulance.

 

Per Motor Trend:

"Putting a tonneau or hard bed cover over your truck is the BEST thing you can do for highway fuel economy. A shell also can help. Since most of these are relatively light, the extra weight must be worth the improvement. This is one reason something like an Avalanche (which has a bed that's partially covered) often gets better highway mileage than an open pickup with the same drivetrain and tires--and weighs less."

 

I ran a snugtop canopy for about 5 yrs and never noticed any gains on any of the three trucks I had it on. I figured that the weight gain offset any gains on aerodynamics.

There was another article I heard about, done by a university, that claimed that canopies and flow thru tailgates were innefective and that the only mods that actually gained were leaving the tailgate down or a rigid type tonneau cover. Even at that gains were pretty insignificant, like in the .2 to .5 mpg range.

Seems like alot of conflicting research to me so do what works for you I guess. I know slowing down from 130km/h to 100 can net me up to a 9MPG gain but I still can't bring myself to change. And 9mpg...that's significant!

 

I didn't notice any increase nor decrease in MPG's before or after my tonnue cover install.

 

Remember, it MUST be highway use/gains as the cover would not come into play until sustained speeds over 55 MPH.

 

From my experience, flatbeds KILL mileage, at least on duallys at speed. My 95 with the pickup bed would regularly get 19-21mpg highway...flatbed mileage is about 18 tops!!! It get's worse the faster you go, and a head or sidewind is really bad!

Also, with the flatbed off, I notice it takes about 1/3-1/2 the boost to hold speed as it does with the flatbed!

Chris

 

I don't doubt that at all. A friend of mine had a shop truck (2001 3500 single cab 6 speed, 3.55 gears) with a flatbed with a lift on the back, HEAVY! IT got 15mpg tops. He took it off to put a regular dually bed on it and drove it for 2 weeks before he sold it and got around 20mpg. I know thats alot of weight difference but that is the same as putting 1,000 pounds of cargo in the bed... You wouldn't lose 5mpg doing that.

 

Exactly!

My Brother's 454 Chevy would do 95-100mph with a regular bed on it. Put a flatbed on, now it strains to do 85mph flat out!!

Didn't hurt the mileage much, but at 10mpg, how could it!

Chris

 

HUH? 19.85mpg last tank hand calculated.

 

I get excellent mileage with my truck,, on the highway at under 120kmph I can go up to 1400km,, or the equivalent of 27 mpg (imperial gallon not sure how that would relate to a us gallon)

Kevin

 

I think he was referring to some people who complain when they don't get 20MPG...not saying that these trucks won't!

Best the 95 ever did was 21.6mpg, and so far, the 98's best is 20.8mpg on the way home from picking it up in Texas! With the new tires, I'm down to about 15.5-16mpg in rural spirited driving

Chris

 

How about one of them fifth wheel talegates. Would that be better or bad on mpg.

 

WAAAAYYY worse. Anything that was lars or louvers will be worse than a tailgat up, down, or off! Each louver makes it's own drag, on top of the wheel wells, bedsides, etc!!

Chris

 

JMO , but driving with the tailgate down makes people look like a dork , JMO!

 

Saw the Mythbusters episode. I think the U of Michigan (?) did some wind tunnel testing in a closed enviroment. Tailgate down and no tailgate added drag. Tonneau cover was most efficient for the testing. No test was conducted with canopy (cap). Next most efficient after tonneau was tailgate with wing. Some or all 1/2ton Chevy's and some Mopar 1/2tons come with a tailgate wing. The wing extends the tailgate and removes drag caused by the bumper. Supposed to add 1/2mpg.