Automotive

The Roof Rack Costs You More Than the Junk in Your Trunk: What to Strip Now That Gas Prices Are Climbing

Gas prices are climbing again, and some drivers are looking for savings in all the familiar places. But the answer may be sitting on the roof of the car, not buried under an old blanket and three emergency water bottles in the trunk.

AAA reported on September 17 that the national average for regular gasoline reached $4.43 per gallon. That price sits more than $1 above the year-earlier average. That makes a permanent roof rack worth another look. A rack, cargo box, or bike carrier can add aerodynamic drag every mile you drive, especially at highway speeds. The extra fuel use may not show up as a separate charge on your gas receipt, but the car still pays for it.

The Roof Has a Bigger Fuel Penalty Than the Trunk

A trunk full of unnecessary stuff adds weight. That matters, but the physics of a roof rack create a different problem.

Air hits the front of the vehicle and flows around the body as the car moves. Add crossbars, rails, a cargo box, skis, or bicycles, and the airflow gets messier. The engine then needs to overcome more aerodynamic resistance, particularly as speed rises. The Department of Energy identifies aerodynamic drag as one of the forces that affects fuel use.

Vehicles do not all react the same way. A tall SUV can hide some equipment behind its bodywork, while a lower sedan can expose more of the rack directly to the airflow. The shape of the rack matters, too.

An Empty Rack Still Does Something

The easiest mistake involves the word “empty.” A driver might remove the skis, bikes, or storage bin and assume the fuel penalty disappears. It does not. Crossbars and rack components still stick into the airflow, creating additional resistance even when they carry absolutely nothing. Consumer Reports found that empty roof racks affected fuel economy in both the sedan and SUV it tested.

That makes the unused rack a strange piece of automotive equipment. It performs a job for perhaps a few weekends each year while potentially adding drag during every commute in between.

Consumer Reports’ more recent fuel-saving guidance also recommends removing unused roof racks and cargo boxes. Its testing found that empty racks could reduce fuel economy by 2 to 5 mpg, depending on the vehicle.

The practical question becomes simple: If the rack has not carried anything for weeks, why keep paying the aerodynamic rent?

The Cargo Box Deserves an Even Closer Look

A rooftop cargo box can solve a real problem. Families can carry luggage without filling every seat and footwell. Ski equipment can stay outside the passenger compartment. A smaller vehicle can handle a trip that otherwise might require borrowing or renting something larger.

But a cargo box creates considerably more surface area than a pair of crossbars. Consumer Reports testing found that a rooftop carrier reduced fuel economy by 19% on the tested Altima. The RAV4 experienced a 13% reduction with the carrier installed.

Those figures came from controlled testing at 65 mph, so drivers should not treat them as a universal penalty for every vehicle or every cargo box. Still, the test illustrates why roof-mounted equipment becomes more expensive as highway driving increases.

A cargo box used for a weeklong vacation makes a different financial calculation from a cargo box that remains mounted from November through March. If the equipment serves a real purpose, use it. If it has become permanent decoration, the garage may be a better parking spot.

Your Trunk Has a Different Problem

Removing a roof rack does not mean every heavy object in the car deserves a permanent home. The trunk can accumulate its own collection of forgotten cargo. A toolbox, sports equipment, several bags of soil, old camping gear, a case of bottled water, and a pile of miscellaneous supplies can add considerable weight. Unlike aerodynamic drag, that weight affects the vehicle wherever it travels.

The Department of Energy recommends removing unnecessary weight because carrying extra mass can reduce fuel economy. It also specifically recommends reducing roof-mounted cargo because it hurts aerodynamics.

That creates a useful distinction. The roof deserves attention because of drag. The trunk deserves attention because of weight. Both increase the energy required to move the vehicle, but they do it in different ways.

A quick unloading session can therefore target both problems. Take out the equipment that only made sense for last season, remove the rack that has sat unused, and leave the items that genuinely belong in the vehicle.

Highway Drivers Have More to Gain

Aerodynamics become especially relevant as speed increases. That makes an unused roof rack more consequential for someone who spends hours on interstates than for someone whose driving consists mostly of short trips around town.

Consumer Reports found notable fuel-economy changes during highway testing with racks, rooftop carriers, and bicycles. In one test, adding two mountain bikes to a roof rack caused a larger fuel-economy loss than several other rack configurations.

Speed itself also affects fuel consumption. The Department of Energy notes that fuel economy generally falls rapidly at speeds above 50 mph. 

That creates a useful reality check. Removing a roof rack cannot erase every factor affecting fuel costs. Traffic, speed, weather, tire condition, vehicle design, driving habits, and trip length all matter. Still, eliminating unnecessary aerodynamic equipment costs nothing once the rack comes off.

Do a Five-Minute Garage Audit

The best time to inspect the car is before the next long drive, not halfway through a vacation. Look at the roof first. If the crossbars, ski rack, bike rack, or cargo box have no job scheduled, consider removing them according to the manufacturer’s instructions. Store the hardware somewhere dry and organized so reinstalling it later does not become an archaeological expedition.

Then open the trunk and passenger area. Remove seasonal equipment, duplicate supplies, heavy tools that rarely get used, and anything that migrated into the car without a reason. Keep emergency equipment and items the vehicle actually needs.

There is another reason to make this a routine. Fuel prices can change quickly. AAA’s September 17 report shows how sharply the national average has moved over a short period. When fuel costs rise, small sources of waste become easier to notice. Drivers do not need a dramatic vehicle modification to respond. Sometimes the useful change involves taking something off.

The Cheapest Fuel-Saving Upgrade Might Be in the Garage

A roof rack makes sense when it carries something that would otherwise create a bigger problem. An empty rack sitting on the roof simply adds equipment to a vehicle that already has enough work to do.

The same principle applies inside the car. Keep what serves a purpose, remove what does not, and pay particular attention to anything that creates aerodynamic drag.

Would you remove an unused roof rack to save fuel, or is the convenience worth the extra drag? Share your thoughts in the comments.

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