A tonneau cover saves more fuel than a topper, but the topper does save fuel as well.
Maybe it’s more entertainment than actual science, but Mythbusters experimented on the gas consumption of pickup trucks with the tailgate up or down. But, they seem to have proven that the tailgate up is the best option.
Using a wind tunnel, they discovered that the airflow creates a rotating pressure inside the truck’s bed, kind of like a sideways tornado, which helps air flow over rather than get caught by the bed creating less wind resistance.
As you can imagine, the pressure created in the truck’s bed acts much like a tonneau cover would. So, we can assume that a tonneau cover will also provide better miles per gallon.
If we turn our attention to the truck topper, there is a noticeable difference in the shape and how the air will flow over it. It also has more weight, and weight impacts fuel mileage. However, some argue that it doesn’t make a difference, and some say they notice up to a two mpg difference.
We can speculate on what has the best fuel economy until the cows come home, but we’ll never have anything concrete without a test.
Fortunately, Snugtop has factual evidence that both tonneau covers and caps save fuel, but there is very little difference between a tonneau cover and a truck cap for gas mileage.
They measured from a standing start to a finish line speed. The first run without a cover or a cap hit 143 mph. When they tested the truck with a tonneau cover, its top speed was 153.9 mph, and when they put the truck cap on, it was clocked 153.5 mph.
Maybe the extra weight of the topper was the reason it was 0.4 seconds slower than the bed cover; we can only assume. But the fact is that tonneau covers and truck caps do reduce wind drag and increase gas mileage with today’s gas prices that can add up to several hundred in savings year. So a tonneau cover at a reasonable price would pay itself off in a year or so if you drive a lot.
In the next video, you can see how wind reacts to the shape of a truck in several scenarios; no cover – tailgate up and down, tonneau cover, truck cap. All be it the cap is not a usual shape, we can still see how the wind reacts to the other scenarios.
Simply put, the tests prove that tonneau covers and truck caps save the same amount of gas when installed.
Of course, the reason for buying a tonneau cover or a cap isn’t based solely on fuel economy; it’s merely a perk. There are many more benefits to owning one or the other, like security from thieves and protection from the elements.
This is a perfect idea if you drive a lot and you’re looking to increase your pickup truck’s gas mileage and need to keep things dry and safe in your truck bed.
I hope you enjoyed following along and have a clear answer to the question, “Which is better – Tonneau VS Cap Gas Mileage?”
Read more from our blog: “Which Tonneau Cover Should I Buy – The Supreme Guide.”