Why does the engine oil need to be changed?

Why does the engine oil need to be changed?

All engine oil loses its effectiveness over time and must be replaced to ensure optimal engine performance.

Let's take a look at what happens to engine oil over time and why you need to change the oil regularly.

Additives - designed to work

Additives are added to base oils to reduce degrading processes in the engine and to improve the beneficial properties of the engine oil. For example, antioxidant additives help slow down the rate of oxidation.

Cleaning additives help prevent deposits and sludge while cleaning existing deposits. Anti-wear additives are added to some lubricants to create a protective barrier on metal components and prevent wear.


Base oils are the basic substance of every lubricant. Over time they lose their effectiveness due to the following factors: oxidation, high heat, humidity, loss of viscosity and fuel dilution.


The interaction between oxygen molecules and engine oil molecules leads to a chemical breakdown of the individual substances. Just as oxygen turns a sliced ​​apple brown or rusts exposed metal, oxygen breaks down base oils and reduces the effectiveness of motor oil.


Today's engines run hotter than ever, with temperatures reaching 113°C.


Your vehicle is permanently exposed to temperature fluctuations, even if it is "only" parked in the garage. These temperature fluctuations lead to the formation of condensation in your engine, which settles in the engine oil, among other things.

Leaving the vehicle for long periods of time or taking short trips that do not allow the engine to fully warm up can allow water to remain in the oil instead of evaporating and escaping through the exhaust pipe. The water in the engine oil can lead to sludge formation.


The viscosity of a motor oil is one of its most important properties. It has a direct influence on wear protection. Your engine is designed to work best with engine oil of a certain viscosity (eg 5W-30).

The intense pressure that oil is subjected to as it is forced between moving parts such as the piston ring/cylinder wall interface can break down its molecular structure, resulting in loss of viscosity.

Over time, the 5W-30 motor oil that your engine was designed for is now essentially a 5W-20 oil and anti-wear protection may deteriorate.


Fuel can be forced past the piston rings and contaminate the engine oil, causing it to lose its viscosity. Frequent short trips that do not allow the oil to reach normal operating temperature can be particularly problematic as the fuel does not volatilize and cannot spill.

Excessive fuel dilution leads to sludge and fouling, necessitating more frequent oil changes.

Why Change Engine Oil
Why Change Engine Oil? Credit: Unsplash


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While every effort has been made to ensure the accuracy and completeness of the information, no guarantee is given nor responsibility taken for errors or omissions in the database. Please check your vehicle's handbook or directly with the manufacturer to ensure you are using the correct oil.