Will Leaving The Tailgate Down On Your Truck Save Fuel?

The myths and misconceptions surrounding automobiles are as old as the automobile itself. Since the dawn of the modern era, people have believed in wild claims centered around various facets of the auto industry. Some of the stranger beliefs include the idea that red cars are inherently more expensive to insure, that all SUVs excel off-road, that ABS always shortens braking distances, and the genuinely outlandish notion that seatbelts are unnecessary in cars equipped with airbags.

While we could have a separate discussion on myths surrounding pickup trucks, one of the most popular beliefs centered around them is the notion that leaving the tailgate down on mean machines (like the Chevrolet Silverado 2500 HD Duramax and the GMC Sierra 1500 Denali) would actually cause them to burn less fuel. Apparently, this belief stemmed from the fact that leaving the tailgate down would cause the air to flow freely around the truck, but is that really the case?

As it turns out, this longstanding myth was comprehensively busted nearly two decades ago in a Mythbusters episode that aired on the Discovery Channel. They conducted a detailed experiment in which it was conclusively proved that leaving the tailgate down would, in fact, have the opposite effect and make the truck consume more fuel.

On the face of it, leaving the tailgate up seemed like a logical way to save a few gallons of fuel. The rationale was that the closed tailgate would act as a barrier and block free-flowing air, leading to increased fuel consumption. However, multiple experiments conducted to test this theory have proven that it doesn't hold true.

The simplest video that explains this phenomenon was uploaded way back in 2011 by Engineering Explained. The video explains that keeping the tailgate down results in the creation of a layer of turbulent air vortex right behind the cabin of the truck. This turbulent air pocket increases the aerodynamic drag on the vehicle, adversely affecting the fuel economy.

In contrast, when you drive around the truck with the tailgate up, the airflow around the vehicle follows an entirely different path. The design of the tailgate and the direction of the car's movement create a bubble of circulating air on top of the truck's cargo bed. This air bubble prevents the turbulent air from hitting the raised cargo bed, letting it flow at smoothly some height above the raised tailgate.

In 2014, another experiment was conducted by Autoblog in collaboration with Ford to check if it was really a good idea to keep the tailgate on pickup trucks. The conclusion of that study wasn't surprising at all; the most fuel-efficient way to travel around on a pickup truck is with its tailgate up.