Gas Millage?
Senior Member
Joined: Dec 2009
Posts: 1,052
Likes: 39
From: Republic of Texas
(1) No, it doesn't.
(2) How do you come up with this number? Show me some equations and physics as to how you arrived at that number. I highly doubt that even if you are correct that you would see a difference of .5 mpg.
(3) Irrelevant, you already see the smoke clearing the gate with it up. The air flow does not immediately dip down below the top of the cab and immediately hit your tailgate. It just doesn't happen, as evidenced by the wind tunnel test and pictures. On a long bed it might come close, but at speed, the pressure difference is more than likely going to take care of most of that.
Don't you think that if it made a difference we'd have retractable tailgates that move out of the way and were ONLY used when you needed to keep things in the bed? That those responsible for designing new features on trucks would have pushed hard to get that into production because they'd get recognition and maybe a bonus for improving economy which will be a big selling point for trucks from here out?
(2) How do you come up with this number? Show me some equations and physics as to how you arrived at that number. I highly doubt that even if you are correct that you would see a difference of .5 mpg.
(3) Irrelevant, you already see the smoke clearing the gate with it up. The air flow does not immediately dip down below the top of the cab and immediately hit your tailgate. It just doesn't happen, as evidenced by the wind tunnel test and pictures. On a long bed it might come close, but at speed, the pressure difference is more than likely going to take care of most of that.
Don't you think that if it made a difference we'd have retractable tailgates that move out of the way and were ONLY used when you needed to keep things in the bed? That those responsible for designing new features on trucks would have pushed hard to get that into production because they'd get recognition and maybe a bonus for improving economy which will be a big selling point for trucks from here out?
Show me there is no differential pressure on the tailgate at 60 or 70 mph and I will believe you. Why is it that the truck manufacturers don't provide that data?
With the video on Ford's big wind tunnel, they talk about the energy in the box and minimize the bubble behind the tailgate. What is that?
And what is the "spoiler" on the tailgate that they refer to? I don't see any spoiler on my F-150 tailgate. Anyone got a picture of that spoiler?
A spoiler would definitely help, just like a slotted tailgate, or tailgate down.
I'm just guessing at .5 MPG improvement for 800 pounds aerodynamic drag reduction. Probably not more that 1 MPG or people would be jumping on that right away.
By the way, I'm in the oil and gas business, so why the heck am I promoting fuel efficiency?
TAILGATES RULE! DOWN WITH TONNEAUS! KEEP YOUR TAILGATE UP! 6" LIFTS FOR EVERYBODY!
Last edited by SailorDon; Jan 18, 2010 at 11:05 PM.
Senior Member
Joined: Dec 2009
Posts: 1,052
Likes: 39
From: Republic of Texas
Senior Member
Joined: Jul 2008
Posts: 427
Likes: 3
From: Kingsville/Dallas, TX
I found this on a tundra site. No i wasnt on it! google found it for me.
The Tonneau Cover Fuel Economy MYTH | tundraheadquarters.com
OUR BS METER WENT OFF when we read that last line. Is SEMA actually saying that they spent the money to test aerodynamic drag on four different trucks, but that they didn’t spend just a little bit more to find out about actual real-world fuel economy savings? Something doesn’t smell right…
Here’s our interpretation of the study:
1) The largest reduction in aerodynamic drag (7.8%) was observed at 85mph. If we’re generous, we could assume that 75% of the engine’s power is being used to overcome the force of drag at this speed (the other 25% goes to tire friction, heat loss, etc.). If drag is reduced by 8%, that would result in a 6% reduction in engine workload. If the truck averages 18 mpg at this speed, then reducing engine workload 6% would improve fuel economy 1.08 mpg. SO, at 85 mph, expect to see about a 1 mpg improvement with a tonneau cover.
2) At a more realistic highway speed of 65 mph, drag is reduced about 5.5%. Using the same math as above but assuming that only half of the engine’s power is being used to overcome drag at this lower speed, fuel economy is improved by 0.5 mpg.
3) At 55mph or below, the fuel economy benefit basically disappears. Aerodynamic drag isn’t significant until you reach speeds of about 55-60 mph. Technically there would be a fuel savings, but it would be small. Less than a tenth of a mpg.
4) Finally, there were 6 different tonneau covers tested. SEMA didn’t disclose which was which, but we’re fairly certain that a fitted, over the rail solid fiberglass tonneau cover gives the best fuel economy results. The cloth/vinyl covers buffet in the wind, and anything that doesn’t go over the rail creates it’s own vortex. Painted to match, these covers cost $700 to $1100 installed.
Now before anyone goes off on us for making assumptions, etc., we did speak with a couple of engineers when writing this article. They emphasized these are rough numbers, and that they could be off by as much as 25%. That means that the best case fuel economy improvement is 1.35 mpg at 85 mph, and 0.63 mpg at 65 mph.
Assuming gas is $3.50 per gallon, here’s how the best case math works out:
Driving your tonneau cover equipped truck at 65mph for 20 minutes per day would save you 0.04 gallons of gas, or about $0.14 per day. Under these circumstances, we figure it will take about 30 years of workday commuting to save enough to earn back the cost of a $1000 tonneau cover.
Drive your tonneau cover equipped truck at 85mph for 60 minutes a day and you’ll save 0.33 gallons of gas, or about $1.16 per day. We figure that’s only 3 years and 7 months of workday commuting to earn back a $1000 tonneau cover. Of course, during that same period, you’ll spend over $13k on fuel. We feel sorry for anyone that has to drive their truck 85mph for 60 minutes a day — the fuel costs for just three years would be enough to buy a nice toy (ATV
, boat, motorcycle, etc.).
Bottomline: Tonneau covers DO save gas, but not very much. While the aerodynamic drag numbers sound impressive (4-8% reduction), they don’t actually result in enough gas savings to justify the expense for a normal user. If you buy a tonneau, do it because it keeps your bed dry and secure.
The Tonneau Cover Fuel Economy MYTH | tundraheadquarters.com
OUR BS METER WENT OFF when we read that last line. Is SEMA actually saying that they spent the money to test aerodynamic drag on four different trucks, but that they didn’t spend just a little bit more to find out about actual real-world fuel economy savings? Something doesn’t smell right…
Here’s our interpretation of the study:
1) The largest reduction in aerodynamic drag (7.8%) was observed at 85mph. If we’re generous, we could assume that 75% of the engine’s power is being used to overcome the force of drag at this speed (the other 25% goes to tire friction, heat loss, etc.). If drag is reduced by 8%, that would result in a 6% reduction in engine workload. If the truck averages 18 mpg at this speed, then reducing engine workload 6% would improve fuel economy 1.08 mpg. SO, at 85 mph, expect to see about a 1 mpg improvement with a tonneau cover.
2) At a more realistic highway speed of 65 mph, drag is reduced about 5.5%. Using the same math as above but assuming that only half of the engine’s power is being used to overcome drag at this lower speed, fuel economy is improved by 0.5 mpg.
3) At 55mph or below, the fuel economy benefit basically disappears. Aerodynamic drag isn’t significant until you reach speeds of about 55-60 mph. Technically there would be a fuel savings, but it would be small. Less than a tenth of a mpg.
4) Finally, there were 6 different tonneau covers tested. SEMA didn’t disclose which was which, but we’re fairly certain that a fitted, over the rail solid fiberglass tonneau cover gives the best fuel economy results. The cloth/vinyl covers buffet in the wind, and anything that doesn’t go over the rail creates it’s own vortex. Painted to match, these covers cost $700 to $1100 installed.
Now before anyone goes off on us for making assumptions, etc., we did speak with a couple of engineers when writing this article. They emphasized these are rough numbers, and that they could be off by as much as 25%. That means that the best case fuel economy improvement is 1.35 mpg at 85 mph, and 0.63 mpg at 65 mph.
Assuming gas is $3.50 per gallon, here’s how the best case math works out:
Driving your tonneau cover equipped truck at 65mph for 20 minutes per day would save you 0.04 gallons of gas, or about $0.14 per day. Under these circumstances, we figure it will take about 30 years of workday commuting to save enough to earn back the cost of a $1000 tonneau cover.
Drive your tonneau cover equipped truck at 85mph for 60 minutes a day and you’ll save 0.33 gallons of gas, or about $1.16 per day. We figure that’s only 3 years and 7 months of workday commuting to earn back a $1000 tonneau cover. Of course, during that same period, you’ll spend over $13k on fuel. We feel sorry for anyone that has to drive their truck 85mph for 60 minutes a day — the fuel costs for just three years would be enough to buy a nice toy (ATV
, boat, motorcycle, etc.).Bottomline: Tonneau covers DO save gas, but not very much. While the aerodynamic drag numbers sound impressive (4-8% reduction), they don’t actually result in enough gas savings to justify the expense for a normal user. If you buy a tonneau, do it because it keeps your bed dry and secure.
Senior Member
Joined: Nov 2007
Posts: 1,980
Likes: 7
From: UT
as for my truck, the INSIGNIFICANT mpg savings would be the same. it would always be the same whether youre getting 5 mpgs or 20 mpgs. the size of my tires doesnt change the aerodynamics of my cab.
Senior Member
Joined: Nov 2007
Posts: 1,980
Likes: 7
From: UT
I found this on a tundra site. No i wasnt on it!
Bottomline: Tonneau covers DO save gas, but not very much. While the aerodynamic drag numbers sound impressive (4-8% reduction), they don’t actually result in enough gas savings to justify the expense for a normal user. If you buy a tonneau, do it because it keeps your bed dry and secure.
Bottomline: Tonneau covers DO save gas, but not very much. While the aerodynamic drag numbers sound impressive (4-8% reduction), they don’t actually result in enough gas savings to justify the expense for a normal user. If you buy a tonneau, do it because it keeps your bed dry and secure.
Junior Member
Joined: Jan 2009
Posts: 11
Likes: 0
From: Zion,Illinois
My 09 in summer is getting 17 to 18 around town with the same engine and on the road it averages 20 to 23 BUT durring the winter it drops to like 15 but I think it's due to idling and seems I have to sit in traffic more
Member
Joined: Aug 2009
Posts: 53
Likes: 0
Mileage
Mine is a 5.4 3v 2wd crew and lately it's been averaging about 17. It has gotten as good as 20.5 on the highway..It seems that the gas locally has changed also because my wife has an explorer that normally gets around 18 and hers has fallen off to about 16. Make sure you reset the MPG indicator at every tank of gas to get a more realistic indicator.