That roof rack is destroying your fuel economy

New study finds roof racks in 2015 were responsible for the consumption of 100 million gallons of gas

Gear News
Roof racks offer unprecedented convenience, but that comes at a high financial cost.

Roof racks offer unprecedented convenience, but that comes at a high financial cost.

For those of with small cars or who frequently carry a lot of gear, roof racks are a godsend. They also look sleek. But as anyone who’s had them before knows, they’re noisy when loaded and can destroy your fuel economy.

To learn more about Consumer Reports testing methodology, visit their website here.

To learn more about Consumer Reports testing methodology, visit their website here.

How bad is the hit to your wallet? When Consumer Reports tested how roof racks affected fuel economy in 2013, they noticed a 5 mpg drop at highway speeds from an empty rack. Adding a bike to the equation caused fuel consumption to jump by 35% compared to their baseline settings.

Hitch mounted bikes can be expensive to install and require drilling into your vehicle's frame, but don’t create as much wind resistance as their roof mounted counterparts.

Hitch mounted bikes can be expensive to install and require drilling into your vehicle’s frame, but don’t create as much wind resistance as their roof mounted counterparts.

According to a new study by Yuche Chen and Alan Meier published in the most recent issue of Energy Policy, “roof racks are responsible for 0.8% of light-duty vehicle fuel consumption in 2015, corresponding to 100 million gallons of gasoline per year.”

They calculated these numbers by crowdsourcing real world data (including forums), watching national highway videos to estimate rack usage, and estimating total vehicle miles traveled.

Their conclusion is that Americans could potentially save hundreds each year by simply unbolting their roof rack until needed. They also suggest that further research into developing aerodynamically shaped bars could help drastically improve fuel economy.

The new study by Chen is stuck behind a paywall, but you may be able to access it through your local library. For a great overview of the material, visit Scientific American.

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  • ColinL says:

    my wagon can’t accept a hitch rack, plus it only really matters on long trips which I take 1-2 times per year. however – the findings are obvious, and much more severe at speeds beyond 65 mph. audi a4 avant (2.0L turbo) gets 26 mpg at 80 with the factory crossbars and light/no wind. add 3 yakima frontloaders, no bikes, and you’re at 24.5.

    put 3 mountainbikes up there and add a 25 mph headwind, and suddenly 17 mpg is all too real. the wind noise is also of a level similar to a regional jet airliner. :)

  • adaycj says:

    My Ford Escape gained 1mpg by removing the factory roof rack. I calculated this by monitoring the MPG over many tanks of fuel both before and after. I can imagine some of the more elaborate, albeit more useful, racks would have a bigger impact.

    The efficiency loss from having bikes isn’t that much of a concern, since most people only need their bikes on the car for a limited time. It is just worth it at that point unless you have other options. I do wonder about the big plastic storage boxes on many vehicles. A local that lives near me has had one on his SUV continuously for years. A kayak or three seems it would really hurt the MPGs too.

  • Chris says:

    The problem is the hitch racks scratch your bike up something fierce. A roof rack protects the bike (as long as there are no low bridges). Around here it is common to see a $4K bike on top of a $2k car. The article / study I think is written around the non enthusiast. But to pay a couple of bucks extra so that your pride and joy stays in top condition is worth every penny to most people reading this. Leaving it on while not in use? That is probably where most of us need to concentrate on changing our habits. It’s not that hard to remove . . . . right?

    • J says:

      Not sure what you mean by “hitch racks scratch your bike up something fierce.” Our rack grips bikes by the tires only, makes it easy to adjust the bikes back and forth to prevent contact, makes it easy to load and unload bikes, as well as to remove and put back on our vehicles. I used to leave our rack on all the time, but it’s nice to have it out of the way when I’ll be loading and unloading stuff. I had a welder fabricate hitches I bolted to the garage wall where I park our bike and kayak racks between uses…convenient, yet out of the way.

    • Patrick says:

      Chris – you may want to look at other hitch racks if you have an issue with their scratching your bike. I regularly transport a $10k road bike, a $8k cross bike, and an $8k mountain bike (you were talking about pricey bikes) with my Kuat NV. This rack has never scratched one of my bikes.

  • jeffreypoirier@comcast.net says:

    On my 2012 Impreza I went from roof to hitch for reasons of noise and mpg. I got rid of the noise, but my gas mileage still suffers with bikes on the back, from 10 to 15%. I miss my Sienna, which could do 4 dudes and 4 bikes all inside with a little work–3 and 3 was easy

    • Tom says:

      Sienna 3 guys and 3 bikes FTW!

      Done that on many a road trip over the decades (well, from Dodge to Honda to Toyota, but minivans rock if your male ego can get over it).

  • Gabe da Silveira says:

    How about if it has a fairing? I know there was a major difference on my Yakima rack before and after the fairing installation. You could really hear the air whipping around the exposed bar before, and after it was silent.

  • Captain Jack says:

    I’ve got a small SUV (Escape) and a roof rack I only use when I have 2 or more bikes… I can get one solo into the back no problem. Reading this I should pull the roof rack off for the times it’s truly needed – but it is kind of a bitch to get it on.

    I had a BMW at one point that had some recessed mounts to quickly add / remove a rack, that was pretty slick… sigh.. #collegetuition

  • MBR says:

    My 2015 Forester only drops from 29-30 mpg on the highway to 25-27 mpg with two bikes on the roof…

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