Signs And Dangers Of Dirty Or Stale Engine Oil

The engine oil performs multiple functions for your car. Over time, the engine oil becomes stale and dirty, and the dirt interferes with some of the oil's functions. The following are some of the telltale signs of dirty engine oil and how it may affect your car.

The Signs

There are various signs of stale engine oil, but the following are some of the most obvious.

Change in Color

Clean oil is lighter in color than dirty oil. When you first pour oil in the engine, you may notice the color is a slightly translucent amber. After some time, the oil picks up dirt particles from the engine and becomes darker and darker. The oil can become so dark that you can't see the dipstick through it when you check the engine oil.

Loud Engine

Lubrication is one of the major functions of engine oil. When the engine is properly lubricated, the oil forms a thin layer between different surfaces of metal so that the surfaces don't actually touch. If the oil becomes stale, its lubricating properties drop, and it may allow different metal surfaces to touch. The friction thus caused by the lack of lubrication leads to noisy engine operations as metal touches metal.

Dirty and Smelly Exhaust

Lastly, dirty engine oil may also manifest itself as dirty and smelly smoke from the car's tailpipe. Ordinarily, the exhaust should be translucent since it's mostly water vapor. If you have not changed the oil for a long time, it may lead to engine damage that may trigger an oil leak. The reaction of the leaking oil and the engine heat is what discolors the exhaust.

The Dangers

Here are some of the dangers to expect if the engine oil is stale or dirty.

Increased Wear and Tear

Dirty oil reduces the lubricating ability of the engine oil and allows different parts of the engine to rub on each other. This metal on metal friction increases the rate of wear and tear of the engine, which is bad for the long-term durability of the engine.


Another function of the engine oil is to cool the engine. Again, the ability of the oil to absorb the heat from the engine reduces if the oil becomes dirty. Thus, the engine may overheat, and overheating is bad for the engine.

Decreased Engine Performance

The efficiency of the engine may also reduce if the oil is stale. This may be partly due to the overheating (the engine operates efficiently within a given temperature range) and wear and tear. You may even experience decreased performance and poor fuel mileage as a result.

For more information, you will want to contact a company such as AutoMedics.