I just recently purchased a fiberglass Tonnea Cover on my 8' foot bed of my diesel powered 2500 Dodge Ram.
I was picking up my TT from the storage lot the other day and bringing the TT home to prep it for our Memorial weekend trip, and was curious about my MPG's as I cruised along around 55 MPH on the freeway.
I hit "reset" on my computer to get the current MPG readout as a towed, and was rather surprised to see readings runing in the low 17's to low 16's as the freeway undulated to little upgrades then leveled or dropped a little. Overall, when I got home my computer summed it up; it was reading about 16.5 MPG's!
Now I know that Myth Busters did the tail gate removed or down versus tailgate up mileage test and found negligible if not better mileage with the tailgate up. The big "but" here is what happens when you have a flat bed height smooth, hard-surface tonneau cover or bed cover? One thing I noticed; was that road noise was much less as the tonneau cover was muffling the noise transmitted through the bed, and that was a positive. It even seemed like the noise of road was muffled greatly while pulling our TT too.
Of course the most startling part was the actual mileage readout. My Dodge computer has been one of those that can be depended on for pretty good accuracy too. I've compared it to actual hand calculations and it seem just about "dead on".
Anyway, obviously the TT was running light, as we hadn't packed it with food, clothing, and filled the water tank. Never the less, once you get rolling resistance overcome, the weight difference between our trailer loaded and not-loaded shouldn't be giving me these big MPG differences.
I really think the tonneau cover is changing something about the way the wind passes over and around our TV and then gets by the TT. The best mileage I got on the flat while towing at 55 MPG was about 15 MPG's. This was 1 to nearly 2 MPG's over that at the same speed on the flat with little or no wind, and the temperature out was 101 degrees! I had my AC going too!
I'm not a wind tunnel, or wind dynamics expert, but I wonder what the air is doing now without an open 8' bed with the tailgate in the up position? Now the truck's rear bed is a sealed rectangular box where the wind now passes over the long box totally with swirling or doing whatever in the bed and around the tailgate and then I assume ramming into the face of my TT, before passing on by.
Anyone here noticed a difference in MPG's when after installing a bed cover?
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Regards, Eightballsidepocket
2005 Dodge Ram 2500 SLT 4x2 Quad Cab, Cummins, 48RE Tranny, Lg Bed, Line-X Spray-on Bed Liner.
06 T25BS Komfort Trailblazer TT
"If you can't say it in person, it isn't worth saying while hiding behind an anonymous P.C.!"
I believe Mythbusters only looked at short bed trucks. . . so YMMV. It would make sense that a light weight cover could help you a little, but probably not as much as you reported in fairly optimum conditions (you were already up to speed when you hit reset). Removing the tailgate is bad because you lose the push from the air swirling back around to fill the low pressure area created behind the tailgate, but you're still getting that in your setup.
There's probably also a psychological variable at play. . . you were conscious of your fuel economy the whole way and wanted to get the highest number you could, so you probably altered your driving style in little ways that you didn't even notice.
My guess is that you'll run for a few more weeks in more diverse driving settings. . . after you've forgotten in the front of your mind that you're going for mileage. . . and you'll remember to check and might see a moderate increase over what you used to get but certainly not the 2 mpg that you experienced on this trip.
2005 Chevrolet Silverado 2500HD Crew Cab SB LS 6.0L 4x4 4.10
DW, DD (born in May, 2007), and me
fickman wrote: I believe Mythbusters only looked at short bed trucks. . . so YMMV. It would make sense that a light weight cover could help you a little, but probably not as much as you reported in fairly optimum conditions (you were already up to speed when you hit reset). Removing the tailgate is bad because you lose the push from the air swirling back around to fill the low pressure area created behind the tailgate, but you're still getting that in your setup.
There's probably also a psychological variable at play. . . you were conscious of your fuel economy the whole way and wanted to get the highest number you could, so you probably altered your driving style in little ways that you didn't even notice.
My guess is that you'll run for a few more weeks in more diverse driving settings. . . after you've forgotten in the front of your mind that you're going for mileage. . . and you'll remember to check and might see a moderate increase over what you used to get but certainly not the 2 mpg that you experienced on this trip.
Actually I set the truck in tow/haul, and cruise just the way I normally tow.
I certainly was hoping that when I hit the reset I wasn't going to see a negative change in MPG's from normal towing MPG's. I do know that hoping doesn't change reality. Reality is reality. I'm a realist in most cases.
Anyway I was encouraged. If anything just the change in road noise being transmitted to the cab was a plus.
Snugtop link
According to many experts, the best way to improve a pickup's fuel economy is to leave the tailgate up and cover the bed with a quality aftermarket Tonneau cover. "Tonneau covers on pickup boxes reduce aerodynamic drag," said Ford's Jack Williams. "We've seen reductions of about 8 to 10 percent on the F150.
The average steady-state cruise control fuel economy improvement at highway speeds is closer to 5 percent.
Over how many tanks of fuel did you compare? I've found with my 4 Dodge diesels since 1992 that the mileage figures from only one or two tanks can be unreliable because diesel fuel seems to foam more than gas, thereby shutting the hose off before the tank is completely full. Whether this matters with the computer I wouldn't know, but it definitely does with hand figuring.
RRUGG
2008 Dodge 2500 QC 4x4 SB Cummins 6 speed auto 3.73
1997 Holiday Rambler 29FK travel trailer
2006 Summit 22RB travel trailer
2003 Dodge Grand Caravan Sport
Bob & Grace professional retirees
Good Sam life members
If I understand correctly you are asking about mileage while towing.
I have put tonneau covers on two pickups and they both gained 1mpg over an open bed, while not towing.
When towing there are many other things at work. With a TT the additional turbulence caused by the open bed and tailgate may actually help your aerodynamics. 'Smoothing' out the airflow at the lower level of the truck bed may cause more of a problem. Adding a full camper shell might help with the TT.
There are so many variables between trucks and trailers it is hard to make a definitive answer.
charlie
2006 Toyota Tundra Crew Cab
2003 Skyline Nomad 24ft Fiver
Me and Wife
Maggie the Old English Sheepdog
Freeman2004 wrote: If you look at the upcoming hybrid truck from Chevy, I "think" I read they will come with a hard tonneau cover to help milage.
In my earlier posts, I directed members to the Snugtop website. At that website they/Snugtop quote a Ford rep. saying that the tonneau cap does indeed increase mileage and decrease wind drag.
I will be heading out this next weekend on roughly a 600+ mile run pulling our TT from San Jose, Ca. to a little above Fort Bragg, Ca. on the Pacific coast. I will most likely be driving against a prevailing Northwest wind on Highway 101 from North of San Francisco to roughly Willits, Ca. and then taking a windy mountain climb to the West to reach the coast and Highway 1, and then proceed Northbound. I'll report in on my mileage.
I will be pulling more weight than when I brought my TT back home from the storage place, and will be carrying extra passengers. However I won't have a full water tank, and will probably only have about 1/3 of it filled so I'm not pulling an additional 800 lbs of fresh water.
I still think my drive from the storage place was not a fluke when I reset my computer to get present-moment MPG's as I was towing in Tow/Haul, and had the cruise set at 55 mph. as I do when towing on a trip. I was showing over a 1 MPG + change! My computer has always been very accurate.
Just bought a 2005 Chevy Silverado crew cab/short bed and I'm definitely going to put a tonneau cover on it. Mostly want it for covering the bed (LOVE my pickup, but going through a little bit of withdrawal from a Suburban) not sure if it will help the MPG, but it sure can't hurt
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