How to inspect a used car in 20 minutes (and when to bring a mechanic)

What to bring

• A flashlight, even in daylight, for looking under the car and into dark corners.
• A paper towel or rag to check fluids.
• A friend, who will notice things you miss.
• Your phone, to photograph anything you want to ask about or have checked.

Walk around the outside

• Stand back and look along each side for waves in the panels, which can mean body repair.
• Check the gaps between panels. They should be even.
• Look at the paint in daylight for mismatched color, overspray on rubber or trim, and rust bubbles, especially at wheel arches and the bottom of doors.
• Check the glass for chips and cracks, and look at the date codes: a single replaced window can mean a break-in or collision.

Tires and wheels

Tires tell a story. Check the tread depth, and look for uneven wear, which can point to alignment or suspension trouble. Check that all four tires match in brand and size, and look at the age code on the sidewall; old tires crack even if the tread is fine. Look at the wheels for curb damage.

Under the hood

• With the engine cool, check the oil: it should be amber to brown, not black and gritty or milky.
• Check the coolant and the transmission fluid, where it can be checked.
• Look for wet spots, drips or fresh clean areas that might hide a leak.
• Look at belts and hoses for cracks, and at the battery for corrosion.
• Ask for a cold start. A car that has been warmed up can hide starting problems.

Inside

• Press every button and work every switch: windows, locks, mirrors, seats, radio, air conditioning and heat.
• Check that the warning lights come on when you turn the key and go off after starting.
• Look at the wear on the pedals, steering wheel and seats. It should match the odometer.
• Smell for dampness, mold and smoke. Lift the carpets and look in the trunk, spare tire well and under the seats for water or rust.

Underneath

With a flashlight, look under the car for fresh drips, rust, damaged or bent parts and anything dangling. A little surface rust on some parts is normal; heavy rust on the frame is not.

When to pay for a professional inspection

Almost always. Once a car passes your own look, have an independent mechanic inspect it, and choose one you trust, not one the seller suggests. It usually costs a modest amount compared with the price of the car, and it can save you thousands. A seller who will not allow it is telling you something.

Common questions