Fluids: Before starting the vehicle, check the oil level and the oil color. Make sure that it isn’t chunky or milky. Oil can be lighter or darker depending on the type used (synthetic or conventional), but it should have a consistent texture. Some people even like to smell the dipstick to see if it smells burnt. Also check the coolant in the radiator and reservoir to ensure there’s no corrosion or lumpiness in the fluid.
Engine sound: There are hundreds of components involved in modern internal combustion engines. Even for the experienced mechanic, it can be difficult to pinpoint certain sounds. But the overall idea is to make sure there’s no loud knocking or ticking sounds coming from the engine. If something sounds weird to you, make sure a trusted mechanic checks it out and gives it the OK before purchasing.
Transmission: During a test drive, be aware of how the car shifts as you accelerate. A solid transmission shouldn’t have any hard shifts, slips, or hesitation between gears.
A/C and heat: It’s easy forget to check the A/C on a used car in the wintertime (or the heat in the summertime).
Exterior lights: Make sure all lights are functional, including turn signals, brake lights, and hazard flashers.
Tire tread: The easiest way to check tire depth is by using a penny. Hold the penny upside down and insert it in the tread. If you can see Lincoln’s hairline, it’s time to replace the tires. If using a tire depth gauge, anything less than 4/32” needs to be replaced.
Undercarriage: Inspect the underside of the vehicle for signs of rust or damage. When it comes to rust on a vehicle a good saying is “if the rust is only skin deep, that’s a vehicle you can keep. But if it affects the frame, that can be a recipe for pain.”
Leaks: Look under the hood for any visible signs of leaks. You can also look at the front undercarriage to see if there’s any fluid underneath. Just be aware that if the A/C is running, it’s normal for condensation to drip underneath the vehicle (it would actually be bad if it didn’t).
Smells: When the engine is running, there shouldn’t be any weird odors coming from the motor or exhaust pipe. Smells are typically a sign that oil, antifreeze, or another fluid is being burnt or leaking.
Codes: If you have access to an OBDII scanner, plug it in and run a diagnostic. Make sure that there are no major check engine codes or incomplete readiness monitors.