How Much MPG Does a Roof Rack Cost?

📋 Quick Facts

An empty roof rack costs 1-2 MPG on the highway. A roof rack with a cargo box or kayaks costs 3-5 MPG. The aerodynamic hit is among the worst per dollar of any accessory.

The data

SAE paper 2014-01-0594 (Chen, GM) measured a sedan with empty crossbars at 65 mph: 1.7 MPG penalty. Add a Thule Force cargo box: 4.4 MPG penalty. The penalty scales with the square of speed - 80 mph is much worse than 60 mph.

Consumer Reports tested a Toyota RAV4 in 2019 with a 19% MPG loss at 65 mph with a loaded roof box. Edmunds tested an F-150 with an empty Yakima rack: 1.4 MPG loss highway, no measurable city loss.

Why the hit is so big

Roof racks sit at the top of the car where air is moving fastest. Frontal area increases significantly, and the bluff shape creates turbulent wake that the engine has to push through. Drag scales with velocity squared - a 10% drag increase at highway speed equals roughly 5-7% more fuel burn.

How to minimize the loss

1. Remove crossbars when not in useMost Yakima/Thule systems are quick-release. Off in 2 minutes, save 1.5 MPG on every highway trip.
2. Aero-shaped bars over square barsThule WingBar Edge, Yakima JetStream - 50% less drag than square bars.
3. Aero-shaped boxesThule Motion XT, Yakima SkyBox NX vs. older square boxes. Up to 40% less drag.
4. Load symmetrically and lowA bike on one side creates more drag than two centered.
5. Drive slowerDrop from 75 to 65 mph and you can recover most of the loss.

🔗 Related Guides

❓ Frequently Asked Questions