If you've ever noticed green-capped stems on tires in a parking lot and wondered why the car's owner chose them, you're not alone. It's a popular question, and one many people answer incorrectly.

We may receive a commission on purchases made from links. Driving on overinflated or underinflated tires is a surefire way to slash the life out of your car's rubber, which is bad news if you're on a ...