Try doing a google search and you will be amazed by the number of hits. Try this and this. This goes against what you would think is common sense, but if you ever have ridden in a pickup bed at highway speed (if you haven't PLEASE DON'T TRY IT) it makes sense. You might also see it if you ever have something in your bed that is a little too light that you forgot to dispose of like a empy trash bag. I've watched them whip around in a vertical circle going down the road. You see it fly up above the bed rails yet it gets sucked back down instead of blown out. These two articles make sense and quote decent sources. You will see numerous articles quoting the opposite, but I haven't found any of them backing it up with wind tunnel testing.

Of course, the improvements they are talking about are only about 5% max MPG or 0.75 MPG for 15 MPG with a hard cover at highway speeds, and only about 1% or .15 MPG for 15 MPG! Not much you can take to the bank, but you sure don't want to do anything to make it worse unless it provides entertainment value of course (insert Lead Foot here)

 

I do plenty of highway driving (150 miles per day, no joke -- it's my everyday commute). And my tailgate is down becuase I have MEASURED my mileage multiple times with it both up and down. I gain about a 1/2 mi per gallon (i.e. from 14.7 to 15.5) with the tailgate down. I too am an engineer and know that TEST DATA from the field is more valid and meaningful than wind tunnel testing. Just remember, the numbers don't lie.

My tonneau cover (Literider by Access) is on order (from 4 wheel online -- never again will I use these guys, I have waited almost a month for this cover. They have my credit card, I have no cover. The first one was delivered damaged, promptly returned and they haven't lived up to their return policy. They were cheap but I guess you get what you pay for, eh). Anyway, I imagine my tonneau will bump me up another 1/2 mpg or so.

2001 Supercrew XLT, 4x4, 5.4L, only mod is a K&N filter, Mobil 1 Supersyn

 

Ive had stuff fly out of my superduty, but did not notice any thing taking off from my one fiddy on hwy.......low cab/high bed seems to keep air flow out of bed?

 

First, off i drive A LOT...A LOT. I bought my truck on January 14th and have 19202 as of today. I drive mainly highway miles. I at least drive 89 a day commuting but then with my job I may have to go 500 miles away on Monday. I had a 00' Isuzu 4x4 Rodeo before my ford and it got about 16mpg. All the time highway/city didn't matter.

Now, my F150 takes a nose dive in MPG in the city to around 13.5-14. But on the Highway at around 60-65 (rural highways mostly) I get around 15.5. The computer is almost spot on with what I figure manually so I stopped doing it manually. I've always heard that taking a tail gate off doesn't actually help MPG, relative to what people think. Well I have done that on a 700 mile trip and I saw no increase.

No for the Extang RT. I bought it needing something that I could take off or roll back at any whim. Also, I didn't want a lot invested in it. I put it on and had to take a trip three days later 500 miles away. I gained a solid 2 MPG with the tonneau on. Since, then I have averaged 1 mpg with the city thrown in there. I would say they really help. just my long winded 2 cents.

 

2004 f150

26000 miles

added cover went from hwy 17.5 mpg to 19.5-20 mpg. This is at 70 mph. If I break 70 this greatly affects my mpg

 

Definate increase in mpg on long trips, no change around town.

 

Just my .02. I had the chance to talk to a Ford Engineer back in 1997. I asked him about the wind tunnel testing on the 1997 pickups. He stated that the testing was done with tailgate up and down. Just as in previous post, he stated with the tail gate up, it should provide better fuel milage.
In the owners manual of my new 05, it states that Ford suggest the use of a bed cover for improved fuel milage. I used to drive a 181 mile trip weekly and came home on weekends. Tried it with my old 1982 F-150 and it didn't seem to make a difference. I took the tailgate off and used a net, and was only able to see a difference in milage if I just slowed down. Nothing else seemed to help. Just driving the speed limit made the biggest difference. (hard to do when you have been gone all week) But the debate goes on!!

 

I have played with this and not found a measureable difference in fuel mileage.
However I have removed the gate stricly for weight reasons when towing.
It weighs 55 lbs.
Looks like I will be looking at a custom built alum panel gate to try to get the best of both weight and dynamics.

 

Had an '02 Screw(bought an '05 screw Lariat) and used ARE's lid. Quality product but of course you will pay. Didn't like Leer or Lund, seemed a little cheesy on stiffeners/supports for the 'glass. Still have the lid if any one is interested: Arizona Beige with ARE's fin and carpeted underside cell# 321-759-3962 Central Florida.

 

Not that this has anything to do with covers, but. I heard that for every 5mph over 70 you drive it is like paying an extra 15cents per gallaon. I have no idea how they calculated this, however I actualy tried driving 70, which is pretty hard for me I'm usaly around 85, anyway my mileage was way better.

 

Somewhere recently an engineering study came out of one of the universities that tonneaus did not effect gas mileage. All I can say is that many years ago I put a vinyl cover on an S-10, drove 70 miles one way every day of the week to school and back, and my mileage jumped 2-3 mpg. As you were running down the road, the front part of the cover would puff up, and the area near the tailgate would dip in. Now being an engineer geek type myself, that tells me that as the air comes over the cab, it is creating a swirl behind the cab, and flowing back down towards the rear of the bed. I think it helps. But if you add the weight with the fiberglass covers, you are probably not going to see any difference.

But they do look goooooooood!

 

I have a Canvas Rollup cover that I really like because of its utility. I didn't see any better gas mileage until I noticed a big difference while pulling a 16 foot trailer with either a Bobcat or other loads, I got much better gas mileage with the cover pulled shut and the trailer connected, with the cover rolled open I got terrible mileage.

 

I have been thinking about this for a while and the answer is it dont matter!!!

Half a mile to the gallon pales in comparison to our driving habits.

I believe my 2003 SCREW gets its best milage at about 63mph.

60mph 1600RPM 26.7 ratio
63mph 1650RPM 26.2 ratio Lower the ratio the better!
65mph 1800RPM 27.7 ratio
70mph 1950RPM 27.9 ratio


DRIVE SLOWER it saves A LOT

I also found that when i keep my RPMs below 2100 while accelerating I keep my milage much higher.

~k_day64

 

Do you watch FOXnews. I think I saw the same broadcast. If you wouls like to know how this is calculated let me know. I will me a math dork for five minutes and write it out for ya

~k_day64

Correct me if I am wrong but every time the piston fires it is comsuming the same amount of fuel regaurdless of RPM? This is an important assumption in the math problem above