Aside from the roof over your head, your car is probably the most expensive thing you own. It’s one of your biggest investments, and to keep it running over the years, you have to take good care of it.

Properly maintaining a vehicle is incredibly important, but it can become an expensive task, especially as the car ages and parts begin to wear out. When things go wrong, you can find yourself stuck with an enormous repair bill.

But with a little planning and know-how, you can avoid being blindsided by a huge invoice from your mechanic:

Change the oil according to manufacturer’s recommendations. Don’t always abide by the old “every 3,000 miles” adage. Read your car’s owner’s manual to see how frequently you should have the oil changed. Doing so more often than is necessary won’t do you or your car any good, it will just make you a little lighter in the wallet. On the flip side, don’t put off an oil change if you’re due for one: You can do serious damage to your car’s engine and wind up spending hundreds on repairs. 

Find someone you trust, and then stick with him. Establish a relationship with a local mechanic, and you’re less likely to be taken advantage of. If your car guy considers you a loyal customer, he may offer you special deals or perform small tasks, like repairing a tire or jumping a battery, at no charge.

Shop wholesale. BJs, Sam’s Club and Costco all offer tires, including mounting, at competitive prices, and installation typically includes lifetime balancing, rotation, and flat repair, which you’d probably pay extra for elsewhere. Call ahead to see if your tires are in stock. If not, they can most likely be ordered. 

Do it yourself. If you know a little about cars, you can save yourself about $600 a year by performing your own light maintenance, like changing the oil, replacing brake pads, flushing your cooling system and changing filters.

Tune up your insurance. Does your car insurance policy cover windshield chip repair? What is your comprehensive deductible? I recently discovered that I could drop my comp deductible down to $0 for less than $60 a year in premium increases, which is a worthy investment because we average one windshield replacement a year, thanks to rocks on the highway.

Be an informed consumer. Shopping around for the best deal might sound like something you’d do for a 3D television, but not for car repair. But Consumer Reports found that the cost of repairs can vary by hundreds of dollars from one shop to another. For a major repair, request a quote from several dealerships or repair shops. Also, beware popular service “rip offs.”

Keep making your loan payment. If your car is paid off, open a savings account and deposit the amount of your loan installment monthly. This way, if your car does need major repairs, you’ve got a rainy day fund to draw from. And if it never does, you’ll have a nice down payment on a new car.