ZeusDriver
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- Joined
- Dec 1, 2025
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- Location
- East Coast, USA
- Vehicles
- 2022 Lightning
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- #1
I can obsess about this stuff... but obviously if I were really concerned about vehicular efficiency, I'd be driving a Prius instead of a Lightning.
So, the theory is this: a tonneau cover lowers the Cd (coefficient of drag) of a pickup truck. That is almost universally true, for reasons that are probably intuitively obvious. The tailgate is an obvious apparent wind catcher. Try to carry a sheet plywood with the flat side facing the wind on a gusty day, and you will appreciate aerodynamic drag.
I've linked a study by SEMA that squares with my understanding of aerodynamics, and especially vehicular aerodynamics.
https://www.agricover.com/downloads/pdf/2007_windtunnel.pdf
Aerodynamic drag becomes increasingly dominant with increases in speed (going up at the square of speed, unlike rolling friction, which stays nearly constant). Power required, therefore, goes up with the cube of speed, (because you are both going faster and pushing harder). Power times time = energy usage. Range increases by the same factor as claimed fuel mileage increases.
If you do a lot of highway driving, (and charge at the robber barons' fast chargers) then a tonneau cover can justify its cost even if you have no other use for it. The range reduction you might imagine from the increase in weight is not measurable, because even the rigid covers are so light. (Do you stick your nose out the window and aim your sneezes backwards to give the truck a little boost?).
My range seemed to improve by about 10 miles (about 5%) after installing my ($100) fold up tonneau cover. However, I was driving fast on the day that I checked, and I don't bother to check on slow driving days, because I know there is no measurable difference. So read the article if you are so inclined, and figure in your style of driving. No "average" gain in range will likely apply to your use case... and my presumed gain won't apply either, unless you happen to drive exactly like me... on the same roads... at the same temperature... in the same wind conditions.
AC and heat have a significant effect on range, as does terrain and many other things. (That is why I used the word "seemed" above -- a definitive, reliable, repeatable test is quite difficult, if not darn near impossible.)
Related: My front air dam extension (the retractable part that extends at 40 to reduce aero drag) fell off a while ago, and I have not been able to detect any difference in range. I tend to drive at close to the speed limit. Maybe if I drove at 20 over all the time, I'd notice a difference.
So, the theory is this: a tonneau cover lowers the Cd (coefficient of drag) of a pickup truck. That is almost universally true, for reasons that are probably intuitively obvious. The tailgate is an obvious apparent wind catcher. Try to carry a sheet plywood with the flat side facing the wind on a gusty day, and you will appreciate aerodynamic drag.
I've linked a study by SEMA that squares with my understanding of aerodynamics, and especially vehicular aerodynamics.
https://www.agricover.com/downloads/pdf/2007_windtunnel.pdf
Aerodynamic drag becomes increasingly dominant with increases in speed (going up at the square of speed, unlike rolling friction, which stays nearly constant). Power required, therefore, goes up with the cube of speed, (because you are both going faster and pushing harder). Power times time = energy usage. Range increases by the same factor as claimed fuel mileage increases.
If you do a lot of highway driving, (and charge at the robber barons' fast chargers) then a tonneau cover can justify its cost even if you have no other use for it. The range reduction you might imagine from the increase in weight is not measurable, because even the rigid covers are so light. (Do you stick your nose out the window and aim your sneezes backwards to give the truck a little boost?).
My range seemed to improve by about 10 miles (about 5%) after installing my ($100) fold up tonneau cover. However, I was driving fast on the day that I checked, and I don't bother to check on slow driving days, because I know there is no measurable difference. So read the article if you are so inclined, and figure in your style of driving. No "average" gain in range will likely apply to your use case... and my presumed gain won't apply either, unless you happen to drive exactly like me... on the same roads... at the same temperature... in the same wind conditions.
AC and heat have a significant effect on range, as does terrain and many other things. (That is why I used the word "seemed" above -- a definitive, reliable, repeatable test is quite difficult, if not darn near impossible.)
Related: My front air dam extension (the retractable part that extends at 40 to reduce aero drag) fell off a while ago, and I have not been able to detect any difference in range. I tend to drive at close to the speed limit. Maybe if I drove at 20 over all the time, I'd notice a difference.
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