What happens to a car engine as it ages? The easy answer: it wears out. The much more complicated answer: certain parts wear out before others. Here's what you need to know about them (and how to keep them healthy as long as possible). 

How does an engine work?

The standard everyday vehicle engine is a reciprocating engine. This means that a series of pistons push down on a crankshaft, which transforms the pushing and pulling motions of the pistons into a rotating motion that is passed on to the gearbox and then to the car’s wheels.

A lot of engine components either reciprocate or rotate at very high speeds and high temperatures. Luckily, modern engines have been designed to handle this fact--the parts that wear out quickly are also (usually) the ones that are easy to replace. The first big thing that's likely to wear out in most vehicles is the camshaft drive belt. If it fails, the pistons can smash into the valves, resulting in a big repair bill. All carmakers have a preset mileage at which the camshaft drive belt should be replaced, and some cars even have maintenance-free chain drives that don't have to be replaced at all.

Spark Plugs

Spark plugs are another thing that need to be replaced at a set interval, as the plugs themselves can burn out or become too dirty to work properly. These are usually a quick fix, as they can be changed like a light bulb. (Unscrew the old one, screw in a new one, and you're good to go.)

Wear and (some) tear is good...

The main wear inside an engine comes from all its moving parts. When correctly maintained, the oil in a car’s engine fills the tiny spaces between the moving parts so the parts themselves aren't actually touching (much like the cartilage in your joints). Some wear does occur, especially in the early days, when the engine is “breaking in.” This is merely the process where all the different parts wear ever so slightly so that they all work smoothly together. That's why most automakers suggest that you not treat the engine too harshly or run it to extreme speeds for the first 1,000 miles or so.

...But be aware of these signs

In the long run, the cylinder bores will wear out the piston rings. These rings keep the oil in the engine from getting into the top of the cylinders where the fuel is being burned. That’s one of the main reasons why old or poorly maintained cars have a dark smoky exhaust – that smoke is oil that has gone through the cylinder heads and then out the exhaust.

The engine’s bearings can also wear out. These are metal inserts in the rods that connect the pistons to the crankshaft. If they begin to wear out, it’s easier and cheaper to replace the bearings (as opposed to the entire rod).

These last two types of engine wear--piston rings and engine bearings--should occur over a very long time period, unless there is some sort of manufacturing defect or a lack of maintenance, such as not changing the oil and oil filter at the prescribed intervals. Oil collects all the tiny bits of metal that can wear away in an engine and the filter removes those bits from the oil flow. So not only does oil keep your engine running smoothly, it also keeps it clean and free of stuff that can increase the wear rates.


Engines do wear out, but unlike in the old days, modern ones can last for a significant length of time if proper maintenance is carried out. You can prevent expensive repairs and keep your engine running smoothly with the DCH Toyota of Simi Valley service department—contact us today for more information.