Topping off your gas tank at your next fill up may not be in your best interest. Here are three great reasons to skip topping off the next time you pull into a filling station.

1. Topping off costs you money. According to the Environmental Protection Agency, drivers who top off at the pump are likely paying for gas they’re not getting. That’s because gas station pumps have vapor recovery systems that feed gas vapors back into their tanks in an effort to decrease air pollution but at the same time likely decreasing the amount of fuel you get.

2. Topping off may damage your car. Fuel tanks need extra room so gas can expand while the car is being operated. Without room to expand, gas may evaporate into the vehicle’s vapor collection system, which can damage the system and produce greater emissions.

3. When vehicles’ fuel tanks are overfilled, gas vapors can escape into the air and produce toxic air pollutants. That adversely affects air quality, which ultimately affects your health.