Tonneau Covers and Fuel mileage

I noticed a slight improvement around town and decent increase on the highway especially with a cross wind. I have a extang solid tri-fold cover.

1stindoor said:

Since we're on the topic...I've been looking at them lately. I've had open bed trucks since 1980, and I like the rails I have on the bed. But I'm starting to look at the "high-dollar" metal rolling type that lock. Since I have a 2500 I'm not expecting any fuel savings, but if anyone has any experience with that type of cover I would appreciate your thoughts.

Click to expand...

Those things are the BOMB! I've had hard folding covers on every truck I've owned since 2011 and if I had to do it over again or next time it will be the collapsible folding type like you speak of. My buddy had one on his last truck and it was so nice how it would collapse almost completely up against the cab. You can carry a lot of things in the bed with that setup that you can't with a hard folding cover. Of course the con is that they do leak some whereas the hard folding models do not. personally I could deal with a small amt of water getting it to have the other convenience. They are also more expensive too.

BOWERSFJ said:

I believe Myth Busters, or Motor Trend, did a pretty extensive test on this one ... If I remember correct, it wasn’t a huge diff either way ... Bottom line is really the issues of cargo security and element protection, and convenience of access ... In other words, do you wanna protect your ****, do you wanna lock up your ****, and would a cover get in the way of puttin your **** in there ...


Sent from my iPhone using Tapatalk

Click to expand...

I recall the Mythbusters episode about this. The effects of the tonneau was negligible. Put a tonneau on if it serves your needs or your desires for aesthetics. Don’t bother if it’s for fuel mileage only.

in another thread i was complaining about the poor tailgate design and this was a reply to that issue ...

IF you believe this is not just smoke and mirrors, then you can see a bed cover would have NO effect because the cab causes air flow that completely misses the bed area with the tailgate up

The HFE (high fuel efficiency) RAM models have a tonneau cover, they also run 3.21 gears and rear-wheel drive. It makes a difference enough for them to note it in the model MPG sticker. All the little things you do have an effect. I drive the V6, 3.21 4x4, a hard tonneau cover and high flow air filter (K and N). I get a solid 22 mpg as my worst tank (mostly in-town) and can climb to 28 mpg on the highway and sit there for hours. These are both hand calculated which is about 1 mpg off from the computer.

Grad12 said:

The HFE (high fuel efficiency) RAM models have a tonneau cover, they also run 3.21 gears and rear-wheel drive. It makes a difference enough for them to note it in the model MPG sticker. All the little things you do have an effect. I drive the V6, 3.21 4x4, a hard tonneau cover and high flow air filter (K and N). I get a solid 22 mpg as my worst tank (mostly in-town) and can climb to 28 mpg on the highway and sit there for hours. These are both hand calculated which is about 1 mpg off from the computer.

Click to expand...

I wanted to add. Weight reduction in conjunction with aerodynamics makes a difference. My big tires aren't the same.size as the spare, making it useless so it's coming off during my next maintenance. Less weight= better mileage.

I have a soft tri-fold and i lose about 1 mpg hwy. I got it to protect the stuff in the bed and to hide from prying eyes. I want to get a hard tri-fold that is flat with the bed maybe that will help. I don't know.

slim chance said:

in another thread i was complaining about the poor tailgate design and this was a reply to that issue ...

IF you believe this is not just smoke and mirrors, then you can see a bed cover would have NO effect because the cab causes air flow that completely misses the bed area with the tailgate up

Click to expand...

What you are not accounting for in these photos is the low pressure air bubble turbulence caused by the tailgate that pushes outer level of air flow to clear the bed. In short with the tailgate up think of a sideways balloon laying in the bed. with a bed cover that balloon turns in to a a rolled sleeping bag at the back of the cab but without the drag of the tailgate. There will always be a low pressure area right behind the cab causing air to circulate back toward the cab..........Just look at your truck after driving on the highway in a fresh snowfall. I can tell you that my 2019 classic with a soft tri fold accumulates substantially less snow at the cab window (around 1 inch in a 12 inch snow fall) then my 2005 F150 did with a hard tonneau cover ("3 to 6 inches" with a similar or less volume of snow fall) which tells me that the air is flowing around and over the back of the cab more efficiently and therefore clearing the tonneau of snow. (the difference is I can see out the rear window in the Ram and I could not with the F150)
I can also add that I saw one of my coworkers trucks whom had not cleaned any snow from his roof before going to work and did not have a bed cover, had snow go from 0 at the windshield to nearly a foot at the back of the cab roof. For me this provided further visual evidence of just how large the low pressure air pocket caused by the tailgate is at the back of the cab as the snow did not curve down it stopped squarely at the back of the cab..

slim chance said:

in another thread i was complaining about the poor tailgate design and this was a reply to that issue ...

IF you believe this is not just smoke and mirrors, then you can see a bed cover would have NO effect because the cab causes air flow that completely misses the bed area with the tailgate up

Click to expand...

One thing about it, that smoke stream doesn’t really show that horizontal rolling vacuum that pulls backwards against that tailgate. Or at least that’s what I’ve been told which is why a lot of people used to run with them air net things or ran with their tailgates down.

But one thing that’s interesting in that picture is that with that shorter bed, the bed’s too short to catch any wind that comes over the cab to dip into the bed and hit the tailgate. Maybe this is why a lot of that held true with the full, 6 foot and especially the more common 8 foot beds back in the day.

But y’all’ve seen those goofy-lookin’ flap things on the back of ****** or dry van semi trailers? The whole point of those is to reduce the drag that I talked about in the first part of this post.



Sent from my iPhone using Tapatalk Pro

2019RamInSC said:

New guy here. My experience and opinion, yes it does. Especially at higher speeds.

I used to have a 1995 Dakota 4X4 with the 318 motor.

With tailgate on the top speed was 102 mph. With tailgate off it went to 107 mph. 107 as I recall was also the limit set by the ECU. So possibly it may have gone faster.

All about wind resistance. Simple physics

Have fun!

Click to expand...

nope, cover makes NO difference in top end or mileage, you're kidding yourself if you believe it does.

slim chance said:

in another thread i was complaining about the poor tailgate design and this was a reply to that issue ...

IF you believe this is not just smoke and mirrors, then you can see a bed cover would have NO effect because the cab causes air flow that completely misses the bed area with the tailgate up

Click to expand...

Now why would you want to bring facts and science into a BS session?

back a few years Myth Busters did this very thing with a pick-up, after way too many ways of trying everything they could to improve millage, gate down, gate up, cover on soft, hard, none of it mattered
at the end of the day it was more or less a wash.... so, if you get better mileage out of it count your blessings as for the rest of us enjoy to newfound ways of using your rams! I know 1300.00 I spent on a cover has been well worth it, I wish I had done it years ago!

2019RamInSC said:

Good article. Found this interesting in that article:

“We discovered that in the computational analysis we perform,” said Bloch. “The most harmful air between the cab and bed was coming over the cab and down through the gap, so we paid the most attention to that specific area.”

So that little gap between the cab and bed wreaks more havoc than I would imagine.......Hmmm Bring out the duct tape

Of course based on my findings. How do I explain this:

"A long-disputed topic among truck owners is whether a tailgate raised or lowered is better for aerodynamics, but Bloch says a tailgate in the up position is more aerodynamically efficient. As air flows over the truck, it falls over the cab and pushes forward on the rear of the truck. With the tailgate down, the benefits of that airflow are diminished."

Hmmmmm

Click to expand...

Picture a super-aerodynamic shaped vehicle, tapered both fore and aft. Put it in a wind tunnel and it would be low drag. Now take a vehicle of the same shape, but cut it in half crosswise and throw away the front piece, making the new leading end be totally flat. Put in in a wind tunnel and it would have far more drag. Now take the same shape and turn it around, with the flat piece facing backward and the nicely tapered end now in the front. Put it in a wind tunnel and it's still not as low drag as the one tapered on both ends - having a flat non-tapered trailing end creates a small low-pressure area right behind it.

The low pressure area makes the truck have to pull harder, using the same principle that helps a plane fly with lift generated by the low pressure area above the wings.

The same is true for a truck. When you remove the tailgate, you create a large low-pressure area right behind the cab. With the tailgate up, air somewhat stays in the bed, reducing (not eliminating) the low pressure behind the cab.

So a truck with no tailgate and with added weight (let's say 75 lbs) inside the truck will get a certain mpg under certain conditions. Add a 50 lb tailgate (removing 50 lbs of the weight to keep the total weight the same) and under the same conditions, mpg will improve slightly, around 2-3%. Now add a 25 lb tonneau cover and remove the remaining 25 lbs. The truck's mpg will again increase slightly, even though in all 3 cases, the overall weight was exactly the same.

You can expect improvement, but not enough to feel, most likely south of 1 mpg.

This was probably 10-15 years ago or longer but I recall seeing an article in a fleet management publication about testing this question. The result was mixed in that it increased fuel economy for certain make/models but had no or negative effect on other make/models. Even the same make/model with a different cab/bed length combination would change the results. None were particularly significant unless you actually had a fleet where a small bit of fuel per truck per day resulted in big changes fleetwide and low rolling resistance tires were significantly more impactful.

So the good news everyone who says it worked could be right and everyone who said it didn't could also be right. The bad news is that it's going to be tough ahead of time to say if your particular configuration will save fuel with any particular bed cover or not.

RamInfo said:

When I had my Dakota I read a wind tunnel evaluation that had been done, focusing on reducing drag and, by extension, increasing mileage on that truck. IIRC, the rankings were:

1. Truck with topper shell (most drag)
2. Bare bed, tailgate closed
3. Bare bed, tailgate open (very little difference with #2)
4. Tonneau cover (least drag)

When those runs were completed, they put a stock open-bed truck back into the tunnel but with mirrors removed. Removing the mirrors had more effect on drag than any change on the bed except for adding a topper shell, which still had the highest drag.

I run a tonneau cover but mainly for convenience in hauling and hiding stuff, and to keep the bed and contents dry.

Best,
DG

Click to expand...

For those of you that have not lived, ie, ridden in a pickup truck in the open bed, the answer is that a tonneau cover does little to nothing to change the aerodynamics of the truck. Sitting in the bed with your back to the cab (here it helps to think of the Subaru Brat) there is really no wind that you feel; however, if you sit with your back to the tailgate you get a VERY strong wind in your face, but nothing below the edges of the bed. Essentially, the air flow over a pickup truck leaves a dead space over the bed and unless your cargo is above the line between the back edge of your cab and the top of your tailgate, there is no air movement.

To make it short - a cover on your bed does no more than add extra weight to your vehicle and virtually nothing to the aerodynamics of the truck.

Ok. Sorry but I am “that guy”.... if you are so worried about fuel economy that you are trying to figure out if a GD tanneau cover gives better mileage, YOU HAVE NO BUSINESS BUYING A PICK UP! Pickups get crappy mileage. If you want high mpg, drive a Subaru or a PRIUS!

I take my truck to the canopy shop to get a tonneau as soon as I buy it. I like keeping my stuff secure and dry and it's also a great excuse to keep from helping people move, if you need something moved rent a uhaul.

If someone were to buy a tonneau cover for the sole purpose of better fuel economy (assuming it actually does improve), how many miles would have to be traveled to save enough money on fuel costs to make up for the cost of the cover before fuel cost savings would even matter?

Remember when Chevy had a fliptail spoiler on the top rear of their cabs?