Separate fact from fiction when you're talking with your mechanic

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It’s easy to feel intimidated by a mechanic who says your vehicle needs a new, um, rotorbeltifyer or a change of translubricator fluid. And you may just fork over the money, especially when the offending part or fluid is jammed under your nose. To help separate myth from reality, we’ve prepared this guide to common comments from car mechanics. (See our guide to car maintenance.)

'You need new wipers.'

This observation is often correct. You may not realize wipers are shot until you’re driving in heavy rain or snow. Replace wipers every six months, or if they streak or miss some areas.

'You need a new air filter.'

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A dirty air filter can rob power from an engine. It’s usually checked at every oil change, but that doesn’t mean you’ll need a new one. Have it cleaned or replaced every 12,000 to 15,000 miles. Not sure if it’s dirty? Remove it and hold it up to a strong light. If you can’t see the light, replace the filter.

'Your brakes are worn.'

A high-pitched squeal may be the first warning. Other signs: the brakes grab or vibrate, and the brake pedal feels soft when pressed. A grinding sound means a replacement is long overdue, and worn brake pads may be damaging the brake rotors. Pads should be checked at least twice a year.

'You need an oil change.'

Most vehicles are designed to go 7,500 miles or more between changes under normal driving conditions. And synthetic oil can last twice as long. Check your car owner’s manual, because changes can become pricey. Say your household has two vehicles that log 15,000 miles per year. If you change the oil and filter every 3,000 miles at $40 each, you’ll pay $400 per year. Drive 7,500 miles between oil changes and save $240 per year.

'Flush the engine coolant.'

Older cars may need a coolant flush every two years or 30,000 miles; many newer ones have extended-life coolant, which can last up to 100,000 miles. A sweet odor inside the car can signal a problem.

'Those tires won’t make it.'

Take a quarter and stick it upside down—with George Washington’s face toward you—into the tread (shown). Replace tires when the tread reaches ⅛ inch—roughly the length of the quarter’s rim to Washington’s hairline. (Check our tire buying guide and Ratings.)

'Your struts are shot.'

Look at the strut. If there’s evidence of fluid running down its side, park the car on level ground, press down on the corner of the car with the worn strut, and let go. If the car bounces more than once, there’s a problem.

Bottom line. Check the owner’s manual for recommended maintenance intervals. If a mechanic suggests changing filters and fluids more frequently than the manufacturer recommends, ask for an explanation and consider getting a second opinion. Need an estimate? Go to our car repairs section to find repair estimates in your area for your vehicle’s make and model.

This article also appeared in the March 2014 issue of Consumer Reports magazine.