How Roof Racks and Cargo Boxes Affect Your Fuel Economy

Ever wondered just how much that roof box is cramping your car's fuel style? Gilbert Smith looked into it recently, and here's the scoop.

So, you just snagged a swanky 2025 Chrysler Pacifica, complete with a snazzy 16-cubic-foot Thule rooftop cargo box right off the bat. Super handy for those epic family road trips or rugged overland escapades, right? Absolutely. But here’s the kicker—those handy rooftop carriers do nibble away at your fuel economy if they’re just sitting up there while you zip around town.

Don’t have a Chrysler? No problem. You can still deck out your ride with roof rails or snag a stylish roof pod without breaking the bank. But keep this in mind: even though they’re great for extra space, they do have a hidden cost. That cost? Your fuel economy takes a hit every time you leave them on your car. A few years back, Consumer Reports did a deep dive into this and their findings are as relevant today as they were then.

Here’s the lowdown: in tests with a 2019 Toyota RAV4 and a Nissan Altima, it turns out the sedan really felt the pinch with just a roof rack. The numbers? An 11% drop in fuel efficiency with the rack and a hefty 19% dive with the pod on top. At slower speeds, the impact isn’t as harsh, but once you hit the highway, that’s where the fuel gauge starts to cry.

Take the Altima, for instance. It usually gets a cool 48 miles to the gallon. Stick a roof rack on, and it drops to 43 mpg. Throw a pod into the mix, and you’re down to 39 mpg. Not so fun when you’re watching the fuel needle, right?

And here’s another tidbit—carrying around an empty bike rack? Minor damage. Load it up with a couple of bikes? You’re looking at a 12% hit to your RAV4’s fuel efficiency. The same goes for the Altima but even worse, up to 25% with two bikes onboard. Ouch.

Now, if you're thinking about just how much this could cost you over time, strap in. Let’s say you’re driving a 2020 Toyota RAV4, averaging about 30 mpg. The EPA figures you’ll spend about $1,500 yearly on gas. Add a roof rack and pod? That could cost you an extra $975 over five years just from the added fuel consumption. Even just the rack’s 2% impact could add $150 to your gas bills.

What about sedans like the Altima? Same story. That 19% efficiency hit translates to nearly an extra year's worth of gas over five years. Not exactly pocket change, right?

And if you're thinking, "Maybe I'll just use a small trailer instead," think again. Those can be even harder on your fuel economy. A lightweight trailer might drop your efficiency by 10% just from the get-go, and heavier ones like the Droplet can cut it by up to 20%.

But hey, there's a simple fix to all of this—just take off the storage when you don’t need it. Yes, it’s a hassle, especially after a long trip when you're dreaming of that hot bath and your comfy bed. But taking a few minutes to clear your car’s roof and tidy up can really help you save on fuel in the long run.

So, keep it simple, keep it clean, and your wallet (and your car) will thank you next time you’re cruising down the highway.