Tonneau cover MPG

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freeswimmingfish

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Hey yall
I put a retractable tonneau cover from Truck2go on my 6.4 2500. I watched the TFL guys vid on their MPG test of cover on/off. They showed an increase of 2+ MPG. Well, I got same results!
While I didn’t take a dash pic of before I put it on, I reset my AVG and it was 14.5 mpg on my round trip commute of about 60 miles (28.5 in am, 28.5 in pm)… after I installed it, I reset again after the install and it was 17.3 mpg on same round trip! I wasn’t able to use cruise control due to Houston traffic, but I did try to drive in similar manor on both days. Not a bad improvement and it looks great!
 

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2003F350

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Unusual to actually get any improvement at all with a tonneau cover at all. With or without on any truck I've owned, I've never seen any noticeable change in mileage long-term.

On my short box trucks, I did see a mileage DECREASE by dropping the tailgate.

On my long box trucks, I did see a mileage INCREASE by dropping the tailgate.
 
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freeswimmingfish

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Unusual to actually get any improvement at all with a tonneau cover at all. With or without on any truck I've owned, I've never seen any noticeable change in mileage long-term.

On my short box trucks, I did see a mileage DECREASE by dropping the tailgate.

On my long box trucks, I did see a mileage INCREASE by dropping the tailgate.
The TFL guys did a tailgate up/down test too, they saw a decrease in MPG.
While I didn’t buy it for better MPG, I’ll take it for sure!
 

2003F350

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The TFL guys did a tailgate up/down test too, they saw a decrease in MPG.
While I didn’t buy it for better MPG, I’ll take it for sure!

Did they do it on short box trucks or long box? Mythbusters did it on short box trucks, I did a wind tunnel lab on a model of a short box truck, but I've never seen actual data or a test of it done on a long box truck - I'd just like to know if my experience was a fluke or if there's something to it with long box trucks. It has to do with the 'bubble' effect of wind flow in the box. With a short box truck, the airflow is such that it creates a 'bubble' in the bed that actually smooths out the overall flow and reduces drag with the tailgate up. Tailgate down, that bubble doesn't form, and drag increases. My thought is that, with the extra 1.5 (average) feet of box, a long box truck doesn't generate the proper bubble, and the tailgate acts as a wall at the back of the truck, which increases drag. BUT without seeing data on it I've got no way to prove it out.
 

PolarisCobra

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I think you may want to try the test a few times to see if you get repeatable results. I believe that I have read (don't remember where) that the shape of todays tailgates (rounded on top, lip at the end) improves mileage more than a cover.
 
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freeswimmingfish

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Did they do it on short box trucks or long box? Mythbusters did it on short box trucks, I did a wind tunnel lab on a model of a short box truck, but I've never seen actual data or a test of it done on a long box truck - I'd just like to know if my experience was a fluke or if there's something to it with long box trucks. It has to do with the 'bubble' effect of wind flow in the box. With a short box truck, the airflow is such that it creates a 'bubble' in the bed that actually smooths out the overall flow and reduces drag with the tailgate up. Tailgate down, that bubble doesn't form, and drag increases. My thought is that, with the extra 1.5 (average) feet of box, a long box truck doesn't generate the proper bubble, and the tailgate acts as a wall at the back of the truck, which increases drag. BUT without seeing data on it I've got no way to prove it out.
Tbh, I can’t remember but I know it was a single cab 1500 Tradesman. Can’t remember the bed size. Here is the video
 
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freeswimmingfish

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I think you may want to try the test a few times to see if you get repeatable results. I believe that I have read (don't remember where) that the shape of todays tailgates (rounded on top, lip at the end) improves mileage more than a cover.
Well, the unfortunate part is, I’ll be repeating this test 5 days a week for (hopefully) many more years!
Lol
 

JoshsRam

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Haha. Naw, I never bought a truck for gas mileage!
This was just an observation.
You could try throwing a Hyundai badge on the truck and see if it increases MPG. It works for the Honda kidz, each "Powered By Honda" sticker is good for at least 50 HP, just ask any of them. I jest, I jest...
 

StateOfMind

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I think back to the Mythbusters episode, but that didn't take in to account the whole butt dyno thing. Thats a good looking tonneau, on a good looking truck. If your initial test showed positive results, stop testing and enjoy
 
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freeswimmingfish

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I think back to the Mythbusters episode, but that didn't take in to account the whole butt dyno thing. Thats a good looking tonneau, on a good looking truck. If your initial test showed positive results, stop testing and enjoy
Thanks!
The TFL guys mention mythbusters. See link above, I like those guys, informative and entertaining.
Testing will continue 5 days a week..er I mean going to work!
 

Taifun7

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Greetings all, currently according to the on board computer I'm avg. 22 mpg. Now wait! Hold on a min. 2020 Laramie edition 1500 2wd 5.7 extended cab with a short bed and a tonneau cover. Yes I use cruise control when I can and like a lot of you, I didn't buy the truck for mpg. Oh by the way this is my third Ram since 1998. The other two were 2500 series 2wd for towing purposes.
The 98 was the old 360 cu in. the 2007 was a 6.7 Cummins Turbo ( what a great truck for towing)
 

ReddJackson

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Before tonneau cover best fuel mileage was 19 mpg, after tonneau cover best fuel mileage is 20.2….used cruise if traffic permitted…2015 Laramie 6.7 Turbo diesel
 

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Jim BB

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I have a 2019 1500 classic 5.7 8spd mega crew 5.7 box with a tri fold hard cover on it combined city hwy i average 16 to 17 Ltr per 100Km (19 Mpg) went from Hamilton Ontario to Nova Scotia averaged 10 Ltr per 100Km (28 Mpg) with cruise on as much as possible driving at around 120 Km (75 Mph) so i figured i get really good milage
 

nwhunter55

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I have experienced the same with my 2020 2500 with the 6.7.
I was getting 22 mpg and now see 24 and 25 mpg.
I am not sure it's all the tonneau cover, but I put it on at 20,000 miles and now have 22,000 and either the motor is more broken in, and the mileage has improved, or the tonneau cover makes a difference.
My truck is a 2500 4x4, crew cab with an 8" bed.
 

rvance

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I've had tonneau covers on 3 trucks and it never made a difference in gas mileage.
 
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I too get about 2mpg better fuel economy with my cover on, especially at speeds over 65. Local highway speeds are 80 here, and while I didn't buy my truck for its gas mileage, I'll take the savings when I can.
 

2003F350

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I have experienced the same with my 2020 2500 with the 6.7.
I was getting 22 mpg and now see 24 and 25 mpg.
I am not sure it's all the tonneau cover, but I put it on at 20,000 miles and now have 22,000 and either the motor is more broken in, and the mileage has improved, or the tonneau cover makes a difference.
My truck is a 2500 4x4, crew cab with an 8" bed.

I took my old cover off my '17 and put it on my '22, and my average tends to stay in the 22-24 range, has since new. I actually don't think I've driven very far with the cover off so I can't tell you what it gets without it. I've only got the 6.5 bed though.
 
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