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GM Engineers Confirm That Holiday Decorations for Your Car Reduce Mileage

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Some drivers delight in outfitting their vehicle with Christmas garb for the holidays — wreaths, candy cane antlers, reindeer antlers, Santa hats, etc. While such gear certainly portrays a festive spirit, it turns out it can also increase your auto’s drag and hamper its gas mileage.

A team of engineers at GM arrived at this conclusion after putting one the company’s most  aerodynamic models, the new GMC Terrain, inside the same wind tunnel used to establish its streamlined design.

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2018 GMC Terrain

2018 GMC Terrain

Joel Ruschman, GM aero performance engineer, articulates the process of the experiment: “In order to determine the air resistance caused by each add-on, we first tested the Terrain by itself to determine the vehicle’s baseline drag value. Next, we put each festive item onto the Terrain individually to see how much drag it added compared to the baseline.”

Here are four takeaways from GM’s findings, based on which holiday decorations a vehicle wears:

  • If you fasten a Christmas tree to the roof of your vehicle, the air creates a 90-pound rush of force while you’re driving. This results in 70% more drag and 30% less efficiency when driving on the highway.
  • If you put a wreath on your vehicle’s grille, this might prevent cool air from flowing to the engine, but it doesn’t create drag.
  • If you strap a bow to your roof, you vehicle will experience 15% more drag while achieving 3.5 mpg less efficiency on the highway.
  • Lastly, even small objects like reindeer antlers and a Rudolph nose are more inhibiting to a vehicle than you might think. A car decorated in these trappings has 3% more drag and a 1-mpg lower highway efficiency rating.

The results are definitely surprising. Hopefully this gives you a better idea of which decorations will provide the least amount of drag for your vehicle this season, to help you maximize efficiency and reduce gas costs while visiting your relatives. Though, if you still choose to sheathe your car in heavy, unwieldy decorations, you’ll be more aware of the aerodynamic science taking place as you drive around spreading Christmas cheer.

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News Source: USA Today