Checking the Engine

You don't need to be a master mechanic to know if something is seriously wrong with an engine. If you can use your ears, nose and eyes then you can save yourself from buying    a bad car. Never buy a car with a check engine light on.

The Oil:

Check the oil. It should be full, not overfilled. Don't purchase a car with highly overfilled   oil. Slightly overfilled is almost always not a problem. Some vehicles like Volkswagens
are more sensitive to overfilled oil (cartalk).

Checking the oil may not tell you much about the car, but if it is a private party sale, then it can tell you about the owner. The only thing high mileage cars have in common is the frequency of the oil change.

Check the oil to see how black it is. This indicates whether or not the owner took care of the car. If the oil is a light amber then it may have just been changed. If this is the case then the oil will not give you any information.

See "The Smell" below for more on oil...

The Idle:

Does the car idle at less than 1000 RPM? It should typically be around 800 RPM. High RPMs indicate a number of different problems. The simple advice is to avoid a car with high RPMs, period.

The Smell:

Your nose may not be trained to identify the difference between anti-freeze and oil but   they both smell bad. Most used cars leak a small amount of oil from either the valve  cover, the oil pan, the front or rear main seal, and sometimes at other random places. Although this is typical, a leak can result in engine failure if gone unchecked.

If you smell antifreeze this is always a DANGER sign. You should never smell antifreeze regardless. If you smell antifreeze then part of the cooling system has been  compromised.

Smoke:

Some small amount of smoke at startup is normal. This smoke should be semi-transparent white to very light blue and should dissipate quickly.   Billows of lingering smoke indicates the serious problem of water in the oil. After the vehicle is warmed up there should be no smoke.

An older vehicle with high mileage may still have some small amount of smoke   indicating wear in the engine. In this case it is better to avoid the car; especially if your state requires emiision testing. If the car is in the range of $5,000 it is best to wait and check our another vehicle. If you don't have a lot of experience with cars, I would take it to  a local mechanic perform an inspection. Ask the mechanic to look at tune-up specific items in addtion to his/her inspection such as the spark plugs, plug wires, distributor   cap, etc.