I previously had a 2006 Ford F150 XLT that was very similar to this: a SuperCrew with four full size doors and a 5.5 foot box. My 2006 had a Leer cap on it. I typically was able to get 12 L / 100 Km. The lowest I ever got was 10.9 L / 100 Km by being quite tender on the gas pedal.
The 2009 at the right scared me a bit with the first fill up. I was getting between 15 and 17 L / 100 Km. Way too high for me. Since the engine was running well and I had already had all the fluids changed, it was my opinion that the high gas usage was due to air drag in the uncovered box.
All of the trucks I have owned previous were covered. My Ford Rangers all had a cap. The first Ford F150 I owned had an ABS textured tilting hard tonneau cover. The second Ford F150 I owned had a cap. All covered, all with "reasonable" fuel economy.
I decided to do some testing. All of my driving in the past week has been with a light foot, easy acceleration, and - where possible - keep the RPMs at or below 2000 rpm.
Best I was able to do was 15 L / 100 Km. Too high.
I then found an inexpensive used vinyl tri-fold tonneau cover. The drive to pick this up is about 103 km. I planned the drive to pick this up so that from my house to the pick up location and back would be exactly the same route, same driving conditions, same weather, same curves and hills, same number of stops, same number of small towns with slower speed limits.
From my house to the pick up location was 102.7 km at 15 L / 100 Km.
From the pick up location to my house was 102.9 km at 12 L / 100 Km.
Quite definitive for me. A net improvement in fuel economy of 3 L / 100 Km. That's a 20% improvement.
In both legs of the trip, my driving was as consistent as possible. My speed was constant on the highways where the speed limit is 80 Km/hr. My speed was 90 Km/hr. I did hold back traffic (most insisting on 100 Km/hr is "normal") – but tough luck, I needed to be consistent for my test. My techniques for going down hills and going up hills was consistent – and same with stops and accelerating after a stop.
20% is a fairly major improvement. Despite the gain, I'll still be looking for other ways to improve fuel economy.
And for the math geniuses out there: at 20% increase in fuel economy - pay back on the tonneau cover is 5 fill ups. And, with each tankful I will be covering an extra 187 km with the same amount of gas as before.
PS. The tonneau cover is an older model made by TruxMart. All of the clamps are inside the box and similar to modern tri-folds. No tools required to install. Best of all, whatever is in the back of the truck is covered and out of view.
UPDATE: August 25 2017 – I posted a link to this article on a Facebook page dedicated to trucks in Canada. Most of the comments focused on the test above attempting to invalidate it. Some even claimed it useless. One person, though, was kind enough to post a link with a research paper that supported the fuel economy savings I experienced. The wind tunnel research paper is here . Studies showing the impact of aerodynamics on fuel economy are available. I recall one that showed the impact of adding a roof rack to a vehicle. Even empty, a roof rack can reduce fuel economy by up to 40%. The purpose of the study was to attempt to get owners to remove the roof rack when not in use. That report is here. And, I also need to point out that despite the "add-ons" to increase fuel economy, the best strategy is still to slow down. I recall the story of a driving instructor teaching all new drivers to use the accelerator pedal like there is a raw egg between the bottom of your foot and the pedal surface. Easy and gentle. Saves on gas.
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