Approx. % increase of mpg while adding bed cover
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Joined: Nov 2015
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From: Great Lake State
Here is a link to the Popular Mechanics article. There are definite problems with it. There are also problems with the Snugtop claim and testing including the 3 click gas fill method.
Ford has been doing Aero testing for 30+ years and the Café standards have made them reduce the Cd of the F150 to get better MPG. I do trust that Ford is telling the truth in the video posted that a tonneau is helpful. It likely does less on the current F150 than it has in the past as the Coefficient of drag has been improved already, so the % improvement will be less.
Ford has been doing Aero testing for 30+ years and the Café standards have made them reduce the Cd of the F150 to get better MPG. I do trust that Ford is telling the truth in the video posted that a tonneau is helpful. It likely does less on the current F150 than it has in the past as the Coefficient of drag has been improved already, so the % improvement will be less.
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According to a 1982 Popular Mechanics article/test A tonneau increased MPG by 9% and a topper increased mileage by 13%. I don't know how reputable the test was but they did try.
I suppose the specific topper you use could drastically affect how well it works. Some, as you say, are indeed square like a brick and others have a bit of slope that leads to the tailgate "fin". My topper has a slope of about 75° compared to the truck back window slope of 90°. I haven't seen any topper manufacturers tout wind tunnel tests. SnugTop was involved in the previously mentioned SEMA testing and seemed to conclude a top speed of slightly less with a cab high topper. They attributed the reduction to the weight.
I suppose the specific topper you use could drastically affect how well it works. Some, as you say, are indeed square like a brick and others have a bit of slope that leads to the tailgate "fin". My topper has a slope of about 75° compared to the truck back window slope of 90°. I haven't seen any topper manufacturers tout wind tunnel tests. SnugTop was involved in the previously mentioned SEMA testing and seemed to conclude a top speed of slightly less with a cab high topper. They attributed the reduction to the weight.
Well, back in 1982, they very well could have improved MPG. Trucks back then didn't go through wind tunnel testing to make them as aerodynamic as possible like they do today. That first video shows the little tricks Ford did to improve airflow over the roof and tailgate, which diminished the effectiveness of a cover.
OK now that's kind of funny that he says a tonneau cover is helpful.
I found this from a SEMA study:
"That means that the best case fuel economy improvement is 1.35 mpg at 85 mph, and 0.63 mpg at 65 mph."
Full article:
http://www.tundraheadquarters.com/bl...-economy-myth/
Cliffnotes: Tonneau covers reduce aerodynamic drag quite a bit at up to 7.8% at 85mph, but that reduction of drag only increases fuel economy AT MOST 1.35mpg at 85 and 0.63mpg at 65mph.
Keeping your tires properly inflated makes a bigger difference. Or driving less than 65mph.
I found this from a SEMA study:
"That means that the best case fuel economy improvement is 1.35 mpg at 85 mph, and 0.63 mpg at 65 mph."
Full article:
http://www.tundraheadquarters.com/bl...-economy-myth/
Cliffnotes: Tonneau covers reduce aerodynamic drag quite a bit at up to 7.8% at 85mph, but that reduction of drag only increases fuel economy AT MOST 1.35mpg at 85 and 0.63mpg at 65mph.
Keeping your tires properly inflated makes a bigger difference. Or driving less than 65mph.
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Joined: Jan 2018
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From: Fleetwood, NC
Senior Member
Joined: Nov 2015
Posts: 1,343
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From: Great Lake State
Way back in 81 Ford discovered that the last 2 ft of bed cover did the majority of the work. Anything over the last 1/2 covered was not measurable. The current 6" tailgate fin is a workable compromise that helps without being obtrusive. Trucks with wheel spats, front spoilers that are an inch from the ground, underbelly plates... will not work for most users.
The previous calculations in this thread guesstimate about 1 gallon saved every 1000 miles driven. Not enough for most drivers to even notice ~ a tenth of a percent. Probably you could do better taking your exterior rearview mirrors off.
The previous calculations in this thread guesstimate about 1 gallon saved every 1000 miles driven. Not enough for most drivers to even notice ~ a tenth of a percent. Probably you could do better taking your exterior rearview mirrors off.
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Joined: Jan 2018
Posts: 28
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From: Fleetwood, NC
I log every refueling and maintenance in ACAR (an app) and I notice fluctuations in miles per tank immediately. I just purchased it a few weeks ago and assumed the dealer did their job, but 3 tires were low on air and I was getting 17.5 mpg for one tank at freeway speeds. After correction, it looks like that was costing me 2.5mpg. I won't know for another week or so, however.