While roof racks are useful for carrying bikes, camping gear, and cargo boxes, they can negatively impact fuel efficiency even when not heavily loaded. The effect becomes even more noticeable at highway speeds or when additional roof carriers are installed.
For many motorists, small maintenance habits such as checking tire pressure or replacing spark plugs are already familiar ways to save fuel. Roof racks fall into a different category because the fuel penalty is tied not only to extra weight but also to how airflow moves around the vehicle.The impact varies depending on the type of vehicle, the shape of the rack, and whether accessories such as cargo boxes are attached.
Added Weight Forces The Engine To Work Harder
One reason roof racks reduce fuel economy is the additional weight placed on the vehicle. The U.S. Department of Energy states that fuel efficiency can decrease by 1% for every 100 pounds added to a vehicle.
Basic aluminum roof rails generally weigh around 15 pounds, while larger full-platform systems can weigh up to 100 pounds. Cargo carriers and mounted accessories add even more mass on top of that.
For drivers covering long annual distances, the added weight can gradually increase fuel expenses over time. Jalopnik noted that commuters driving roughly 15,000 miles per year may feel the effect more noticeably than drivers who use their vehicles less frequently.
The overall impact depends on the size, shape, and weight of the vehicle itself, meaning fuel economy losses are not identical across all models.
Aerodynamic Drag Has A Larger Effect Than Weight
While added weight contributes to higher fuel consumption, aerodynamic drag appears to have a much greater effect. Roof racks disrupt airflow around the vehicle, especially at higher speeds.
According to Edmunds, GM technical fellow for aerodynamics Max Schenkel explained that reducing a vehicle’s drag coefficient by 0.01 can improve fuel economy by approximately 0.2 mpg.
The opposite happens when large roof-mounted accessories are installed. A hard-shell cargo carrier can reduce fuel efficiency by as much as 8% during city driving. At moderate highway speeds, the loss can climb to 17%, and at 75 mph it may reach 25%.
Even empty roof racks can create additional resistance against airflow. Once carriers or cargo boxes are added, the aerodynamic penalty becomes substantially larger.
Real-world Tests Showed Fuel Economy Losses Across Vehicle Types
Consumer Reports testing highlighted how different vehicles respond to roof-mounted equipment. During tests conducted at 65 mph, a 2019 Toyota RAV4 equipped with a roof rack experienced a 2% drop in fuel economy.
A 2019 Nissan Altima sedan tested under the same conditions saw a larger 11% decrease. When roof carriers were added, the reductions became steeper for both vehicles.
The RAV4 recorded a 13% decline in fuel economy with the carrier installed, while the Altima dropped by 19% at the same speed.
Drivers should remove roof racks and carriers when they are not needed. For some owners, especially those who rarely use the equipment or drive shorter distances, the fuel savings may be limited. Still, for regular commuters and highway drivers, reducing drag and excess weight can help lower fuel consumption over time.
