How Much Does the Roof Rack Affect Fuel Savings?

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  • In our 75 mph highway fuel economy test, we found our long-term Kia Carnival’s fuel economy improved by 3 miles per gallon (or 12 percent) with its factory throttles removed.
  • Having the bars hang over the airflow increases aerodynamic drag, which further hurts fuel economy the faster the vehicle goes.
  • Our results with the bars removed equate to an increase in highway driving distance of about 60 miles and a fuel cost savings of about $14 every 1000 miles based on current national average gas prices.

During our long-term testing of the 2022 Kia Carnival, we were initially disappointed by the fuel economy we observed. Speculating the bar was factory installed, a $360 option, to be the culprit, we opted to remove it to see how much difference it made. Removal takes approximately 10 minutes and all tools are included: remove the end caps on both sides of the bars and loosen the clamps that attach the bars to the roof rails which are included on the SX and SX Prestige trim levels. Upon release, we immediately saw improved efficiency numbers, prompting us to make a second attempt at a 75 mph highway fuel economy test. On the second run, we beat our previous effort by 3 mpg (25 mpg to 28 mpg), a 12 percent increase and also better than the EPA’s road figure of 26 mpg.

Although the units fitted to our Carnival are shaped to be aero-friendly, they still reduce their ability to slice air. This increase in drag increases exponentially as speed increases, so driving around town will result in lower fuel economy than driving on the highway.

The extra 3 mpg we got after parting ways with our bars meant a roughly 60-mile increase in highway driving range, from 470 to 530 miles. Hypothetically, if a driver were to go on a 1000 mile road trip, this would allow for only one stop of fuel when starting off with a full tank compared to two stops with the bars engaged. And use current national average gas prices, overall fuel costs will also be reduced, with a savings of $14 every 1000 miles when using regular 87 octane fuel. Stretching over a year, and assuming half a mile of driving is completed on the highway, a driver can see nearly triple-digit savings based on US Department of Transportation Federal Highway Administration 13,476 average annual mileage. That’s roughly enough to cover a full year of Disney+ subscription.

carnival kia with factory roof rails and bars

Michael Simari|Car and Driver

Carnival’s increased efficiency doesn’t really get him into world-beating territory. The new Toyota Sienna and Chrysler Pacifica eHybrid hybrid we tested leads the pack among minivans at 33 mpg, with the Sienna’s figure slightly more impressive considering our test car has all-wheel drive. Taking home bronze was the petrol-only Pacifica at 31 mpg, followed by the Honda Odyssey at 30 mpg. Even with this newfound efficiency, the Carnival remains last relative to other minivans in our road fuel economy tests. However, the ultimate driving range is a different story. The Kia, barless, trails only the Toyota in that category, and by only 10 miles (530 and 540 miles, respectively).

Of course, attaching a cargo hauler, kayak, paddleboard, or other bulky accessory to the bar will reduce fuel economy by an even greater amount. But the point is, it takes a few minutes to remove the bars when you’re not using them.

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