If you're one of the millions of Americans about to take a road trip for Memorial Day Weekend, there's an easy way to save money at the pump.  

Dan Zielinski with the national Rubber Manufacturers Association says the winter causes a lot of potholes, and that means your tires are probably under-inflated which could affect your gas mileage.

"One way you can save money at the pump is to make sure your tires are properly inflated, and here's how it works: I mean imagine if you had a bicycle with under-inflated tires, think of how hard your legs would have to work," Zielinski said. 

And he says, this is how you do it.

"Check for a label on the driver's side door or the owner's manual. Check the tires when they're cold before you drive, because when you drive they warm up," he said. 

A recent study by the RMA says only 9 percent of vehicles had all four tires properly inflated.