Fuel economy is a big deal, so automakers spend a huge amount of time and money to ensure cars are as aerodynamic as possible. The smoother the flow of air over a vehicle, the less resistance the car encounters, and the better the fuel economy it achieves. All that time and money goes right out the window the second you trick out your ride in Christmas decorations.
We’ve all seen these festive cars out on the roads before the Thanksgiving turkey even has a chance to cool. They have reindeer antlers on the side windows and fuzzy red Rudolph noses strapped to their grilles. Sometimes there are whole Christmas wreaths complete with decorative pine cones and bows attached right to the grille. It’s all very cute, but it isn’t so great for your car’s aerodynamics and fuel economy.
GMC decided to prove it to you with the help of its engineers and a 2018 GMC Terrain. They took the SUV to the Lockheed Martin low-speed wind tunnel in Smyrna, Georgia and performed tests with assorted Christmas bits attached.
First, they showed how the air flows over the Terrain when it’s not decked out, and then they showed how wonky that airflow gets with Christmas decorations on the car. You can see it go from a nice smooth stream to something broken and uncontrolled.
Their testing demonstrated that a Rudolph nose and antlers reduces your fuel economy by 1 mpg, which isn’t too bad. The wreath, however, despite being this giant thing on the front grille, doesn’t hurt fuel economy at all.
They also put a big floppy bow on the roof. Surprisingly, this decreased fuel economy by 3 mpg. You might want to rethink dressing up your car like a giant Christmas present before you head out for that family road trip.
The worst culprit isn’t a surprise at all. Strapping a Christmas tree to your roof doubles the amount of drag on your car, so plan accordingly if your favorite tree farm is somewhere out in the boondocks.
If you do decide to decorate your car for Christmas, just be sure everything is tightly secured. No one wants a rogue antler smacking into their car as your drive down the highway. You might lose a little fuel economy, but the holiday season is a short one so go ahead an enjoy.