Yakima JetStream Roof Rack On Kia Sorento Plug-In Hybrid Minimally Impacts Fuel Efficiency

The magazine that did this test was none other than Car and Driver, that storied, infamous outlet of pedal mashing glory that so entertainingly educates us about how terribly inefficient cars can be when driven like we stole them. Their findings for the factory installed crossbars on the Kia Carnival (a vehicle somewhat similar to my Sorento PHEV) were interesting in that they confirmed a 12% drop in fuel economy with the factory bars installed on their 75 MPH fuel efficiency test for the Carnival.

I have aftermarket Yakima brand JetStream crossbars on my Sorento, and they stick out about 8 inches on either side of the vehicle, compared to the factory bars. That means they should have slightly more drag. However, the Yakima JetStream bars are purposefully aerodynamic and shaped like teardrops or small “wings” atop my vehicle.

To test whether I saw a similar drop in fuel efficiency, I drove my Kia Sorento on a familiar loop of over 20 miles that is approximately half on 60 MPH freeway, one third on 40 MPH rural highway, and the rest on 25-35 MPH suburban side streets.

My results contradict what C&D found in their piece, but I believe I know why this is the case. First, I drove between 55 and 70 MPH on the 10+ miles of the freeway portion in both trips though the loop, and for most of that distance was driving closer to 55 (only getting to 70 MPH for less than 1 mile). I drove about 45 MPH on average through the rural highway section, and finished the rest of my loops at 35 MPH or less, 100% via the electric only mode (because I could).

Next, I drove alone, with the heated seats and steering wheel on and the music pumping. In addition to my crossbars in place (on the first drive only), I also had Blizzak Winter tires mounted on my Sorento (on both legs) and the temps were in the upper 40’s Fahrenheit. It wasn’t quite ideal in terms of efficiency, but pretty good overall for the first half of February. Regardless, these things potentially dragged me down a little on my energy use.

On my second trip through the loop, I came out faster by 2 minutes. This could mostly have been due to how many lights I hit/how long I was stopped at lights, or in part due to what felt like slightly faster freeway and rural highway legs (slightly less traffic/better flow). In any case, the difference in efficiency was negligible between these two runs.

I only saw a 2-3% difference in efficiency between my two runs (in favor of the run without a roof rack installed). A difference within the margin of error makes it a bit harder to accept, and perhaps running the Sorento on electricity only is inherently more efficient and the reason I saw a smaller difference, but that would only prove that hybrid powertrains are less impacted (and I don’t think that is a safe assumption to make).

Rather, I think the main reason my difference was only equal to about 2.5 miles of additional (electric) range or about ⅕ the difference that Car And Driver saw is simply because my average speed through the course was lower. Even though roughly half of each drive on the course was at freeway speed, the parts that were not likely saw no substantial difference in the fuel efficiency results I saw in each trip through the loop. Thus, speed makes almost all the difference, really. If I extrapolate the 2-3% difference that I saw to a drive using the full charge of the battery and a full tank of gas, I might expect to see an additional 8-12 miles of range.

Finally, I think this suggests that if you are using the factory crossbars on your Kia, and you are concerned about your fuel economy on long highway trips, consider driving a little slower (try the speed limit) and you’ll almost certainly see better results. If you’re shopping for aftermarket crossbars, look for those that might be more aerodynamic too, if you want to keep efficiency losses down. From this and other testing I have done, I am also now fairly certain that my crossbars would fare better than the factory ones did in these tests.

What do you think, readers? Do you agree the slower speed is really what made the difference? I think it does. Please leave your comments and questions below.

Image courtesy of Justin Hart.

Justin Hart has owned and driven electric vehicles for over 15 years, including a first generation Nissan LEAF, second generation Chevy Volt, Tesla Model 3, an electric bicycle and most recently a Kia Sorento PHEV. He is also an avid SUP rider, poet, photographer and wine lover. He enjoys taking long EV and PHEV road trips to beautiful and serene places with the people he loves. Follow Justin on Twitter for daily KIA EV news coverage.