A mechanic shows how he inspects a used car before buying it.

Pro mechanic Scotty Kilmer shows us how to quickly check a used car for purchase. He's been a mechanic for 49 years, so he knows a thing or two about cars.

Here are the takeaways. Also download the free checklist to print out and take with you.

Scan for error codes

Consider getting an OBD II scanner so that you can check the car's computer for any error codes. You can find them for under $40. A popular model is the Blusmart OBD MATE.

All OBD II scanners should work with any car 1996 or newer in the US. Just plug the scanner in, usually at the base of the steering wheel, and then start the car.

First check for error codes using the option "read codes" on the scanner. You want no errors. If any errors show up, that means there's some trouble with the car.

Next check the "drive cycle monitor" and make sure that all monitors are OK. This will help you catch problems, even if the owner cleared the error codes by resetting the computer.

Check under the car

Park on a flat surface and check underneath for any leaks on the ground. Then jack the car up and look at the parts from underneath. Check the CV joints – the gasket between the axle and each wheel – under the engine and under the transmission. Everything should be bone dry.

Check the tires

While you have it jacked up, pull front tires in all directions. The should be solid with no play. If they wobble back and forth, that indicates suspension wear.

All four tires should be worn evenly. There should be no cupping and the tread on the inside and outside of the tire should be roughly the same depth.

Check body for damage

Check all the seams to make sure they are even along the seam and that seams on opposite sides of the car are the same width. Any inconsistencies may indicate an accident.

In particular, check the left and right seams around the hood while it's closed, check all the door seams on both sides of the car, check the seams in and around the trunk, and check the seams under the carpet in the trunk.

If all that looks OK, then walk around the car looking for dings. What you should be looking at is the reflection on the body of the car. A ding will distort the reflection. Dings aren't as serious as structural damage or mechanical problems, but you might negotiate a discount for any dings you point out.

Test drive

Test it for 10 miles on the highway and 10 miles off. Listen for strange noises, check if the car shakes, and whether it pulls to one side while steering wheel is centered.

Pay for final inspection

If all those checks are OK, the last step is to have a professional mechanic do the final inspection. It should cost $80-90.

That's a small price to pay for the extra insurance. It's a drop in the bucket considering you're saving thousands by buying a used car. Doing the initial check saves you from having the mechanic check out an obvious problem vehicle.

Free printable checklist

It's hard to remember all that. Don't forget to download the free checklist to take with you car shopping.

Download the Free Checklist... So You Don't Buy a Lemon

Print out the free Used Car Inspection Checklist. Take it with you car shopping, so you don't make a mistake that costs you thousands of $$$.