Lyft, the Uber competitor, recently enlisted drivers to put a pink car mustache on the grille of their cars before picking up customers. But little did they know that the mustache on cars, according to one expert, potentially causes serious damage to them while on the road.

According to a report from GeekWire that cites Jim Leonard, a service advisor at an independent car repair shop in Bellevue, Washington, the pink “carstaches” could cause temperature problems.

“If the mustache replaces the over-the-air intake of the grille of the car, it’s constructed in such a way air can’t pass through it. If this blocks the air intake to the radiator, it could cause the engine to overheat,” Leonard said. He added that the engine could be seriously damaged if the temperature of the coolant in the radiator continues to go up.