What to check on a test drive

Ask for a cold start

A car that has been warmed up before you arrive is a car whose cold start you cannot judge, and cold start is where an engine is least able to hide anything. Ask for it to be left overnight, or at least for a few hours.

Listen for knocking or rattling in the first few seconds, and watch the exhaust. Blue smoke suggests oil, white that hangs in the air suggests coolant, black suggests fuelling. A brief puff of vapor on a cold morning is condensation and means nothing at all.

Drive a route, not a lap

You need three things in one drive: stop-and-go traffic, a rough surface, and a stretch at 55 mph or better. A vibration that only appears at highway speed will never show up on a residential street, and it is the difference between a wheel balance and a driveshaft.

Brakes, steering, transmission

Brake firmly from about 40 mph where it is safe and empty. The pedal should be firm and consistent — pulsing usually means warped rotors, a pull to one side means a caliper or a hose, and a low soft pedal means air or fluid.

With a light hand the car should track straight, and the wheel should return to center after a turn. Clunks over rough surfaces are suspension bushings or links.

For the transmission, note how long it takes to engage from park, whether it shifts cleanly under both light and hard throttle, and whether it hunts between gears on a gentle incline. Flaring — revs rising between gears — is worth walking away from.

The checks people skip

These take about two minutes together, and they are where most unpleasant surprises actually live.

• Heat AND air conditioning. Winter buyers skip the air conditioning and find out about it in June.
• Every window, lock, mirror and seat adjustment, including the ones you will never use
• All exterior lights, with someone standing outside to confirm — reverse and brake lights included
• Wipers and washers, and whether the blades merely smear
• Pair a phone to the infotainment rather than assuming Bluetooth works
• The DOT date code on each tire: four digits for week and year. Rubber ages out at roughly six years whatever the tread depth says, and mismatched dates mean tires were replaced one at a time.

Afterwards

Open the hood again while everything is hot and look for fresh seepage around the valve cover, the hoses and the front of the engine. Then look at the ground where the car had been sitting before you drove it. Drips that were not there when you arrived are worth a question.