GM Proves That Putting Holiday Decorations On Your Car Is Dumb


Celebrating Christmas really hurts your fuel economy.

We are at the time of year when people love to decorate their homes for the holidays. Christmas lights look great on a house, but decorations seem a bit silly on a car. We have seen tons of cars driving around with those ridiculous reindeer antlers on the sides and a red nose hanging in the grille to make a car look like Rudolph. As it turns out, these decorations may have more negative side effects other than looking kind of dumb. General Motors has set out to scientifically prove these decorations are a big drag.

When we say a drag, we mean a literal aerodynamic drag. GM took its latest GMC Terrain to a wind tunnel to see how Christmas decorations impacted fuel economy. The results indicated that the reindeer antlers caused a 3% increase in aerodynamic drag at highway speeds. This translated to around a 1-mile-per-gallon decrease in fuel economy. The roof-mounted bow-tie was much worse, with a 15% drag increase an 3.5 mpg decrease in highway fuel economy. The worst offender was the roof-mounted tree, which caused a 30% decrease in highway fuel efficiency and a 70% increase in drag coefficient. GM found that the air pushed the tree with around 90 pounds of force.

Fortunately, most people only drive around for a short period of time with a tree on their roof because doing so can seriously effect a car's efficiency. According to the study, the grille-mounted wreath was the only decoration that didn't effect aerodynamics, but it may reduce cooling airflow to the engine. "It might be best to let Rudolph lead Santa's sleigh instead of your ride this holiday season," said Joel Ruschman, GM aero performance engineer.

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