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Engine Oil Selection: What Does Viscosity Mean, Which Oil to Use When?

  • Writer: parcacimreisotomot
    parcacimreisotomot
  • May 7
  • 2 min read

Engine oil is like the life fluid of the engine, which is the heart of your vehicle. Choosing the wrong oil not only reduces engine performance; it can also lead to serious malfunctions in the long run. However, technical terms such as “5W-30” that you encounter when choosing oil can be confusing for most users. In this article, we will discuss in detail the meaning of these terms, the tricks of choosing the right oil, and how to proceed according to the season.


What is Viscosity?

Viscosity refers to the fluidity of the oil. Low viscosity oils are thinner and more fluid, while high viscosity oils are denser.

  • A statement like 5W-30 is in two parts:

    • 5W (Winter): The fluidity of the oil when cold. The lower it is, the faster the oil circulates when the engine is cold.

    • 30: Thickness of oil when engine is running hot. The higher it is, the more protective it is at high temperatures.


Which Viscosity to Use When?

Temperature Range

Recommended Viscosity

-20°C and below

0W-20, 5W-20

-10°C to +10°C

5W-30

+10°C to +30°C

10W-40, 10W-30

+30°C and above

15W-40, 20W-50

The most preferred ones according to Turkey's climate: 5W-30 , 10W-40


Types of Engine Oil

  1. Mineral Oils:

    • Naturally based, generally suitable for older vehicles.

    • It is cheaper but requires more frequent replacement.

  2. Semi-Synthetic Oils:

    • It has both mineral and synthetic properties.

    • It is balanced in terms of price/performance.

  3. Fully Synthetic Oils:

    • It is produced with high technology.

    • Ideal for high-performance and new generation vehicles


    Engine Oil

How to Choose the Right Engine Oil?

  • Read the vehicle owner's manual.

  • The engine type of your vehicle (gasoline, diesel, turbo, atmospheric) is important.

  • Age and mileage: Thicker oils (e.g. 10W-40) may be preferred in vehicles with high mileage.

  • Driving style and frequency: Fully synthetic oil is more gentle on vehicles used in heavy traffic.


Engine Oil Change Frequency

Oil Type

Recommended Variation Range

Mineral

5,000 – 6,000 km

Semi-Synthetic

7,000 – 8,000 km

Fully Synthetic

10,000 – 15,000 km

How to Identify Quality Engine Oil?

  • Must have API (American Petroleum Institute) and ACEA (European Automobile Manufacturers Association) certificates

  • Manufacturer approval codes: Values such as VW 502.00, MB 229.5, BMW Longlife-04 should be sought.

  • The risk of counterfeit products is reduced if the packaging is closed and the label is intact.


Common Mistakes

  • The misconception that “I should put thicker oil, the engine will be better protected”

  • Adding oil of different viscosity as the oil decreases

  • Use summer oil in winter and winter oil in summer


Conclusion: Engine Health Starts with the Right Oil

Choosing engine oil may seem like a simple process, but it determines the life of your engine in the long run. With the right viscosity and quality oil, you can both protect your vehicle and maximize its performance. To learn the right oil for your vehicle, be sure to review your service booklet or consult a reliable mechanic.

 
 
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