Tires lose pressure in the winter when temperatures are colder, about a pound per square inch for every 10-degree drop.
Jon Linkov, Consumer Reports, says "If you haven't checked your tire pressure since the warm weather, your tires could be underinflated by five or more pounds per square inch."
Look how much trouble this minivan is having with underinflated tires in Consumer Reports' emergency handling test.
But with the tires properly inflated, the driver has no problem.
It can be confusing to figure out how much air pressure your tires need. Don't go by the number listed on the sidewall, that's the maximum inflation pressure. The correct pressure is listed in your owner's manual, or you can find it on the doorjamb.
And underinflated tires cost you more money. They wear out sooner. And they hurt your gas mileage.
So how often should you check your tires? At least one a month.