Cars don't last us nearly as long as we'd like. After a few years, depending on how much you drive, your car may already be in need of trading in. But it doesn't have to be this way. With proper maintenance, you can keep your car running smoothly long into its old age.

From MSN, consider these four tips from Doug Newcomb on how to make your car last longer:

Don't forget to change air filter

Even the most mechanically challenged drivers know to change a car's oil and oil filter on a regular basis — even if they don't always do it. But other fluids and filters also need regular maintenance. For example, changing your air filter helps your car breathe easier and the engine last longer. "If your air filter is clogged, your engine is not performing properly," notes Jack Nerad, editorial director and executive market analyst for Kelley Blue Book. "It also hurts your fuel economy, and it can harm the engine over the long term."

Keep it cool

Maintaining your car's cooling system and the proper coolant level is as important as making sure the engine is well lubed and can potentially save you thousands of dollars in repairs. "A cooling-system failure can result in your engine literally melting down," Nerad warns. "Because of lack of proper coolant and maintenance of hoses, you can have major problems."

Tires are often the most neglected part of a car, Nerad adds.

"Most people don't pay much attention to keeping their tires at the right inflation pressure," he says. "And it's not only bad for the car, the tires and fuel economy, but it's also a safety issue. The simple step of keeping the tires up to proper pressure is valuable all the way around," he adds, "and it essentially costs almost nothing."

Know your mechanic

Find a repair shop and mechanic you trust. "And let that shop service your car all the time," says Dave Jones, owner of Jones Automotive in Green County, Pa., and co-host of the Web site AskAutoPro.com. "When you get sick you don't go to a different doctor every time. Your doctor knows you from top to bottom, inside and out."

A good mechanic will get to know your car and look over it the same way, Jones adds.