What is Engine Oil and its Function?

Engine oil is a lubricator used for internal combustion engines that ensures healthy operation of the engine. It protects the moving parts of the engine, reduces friction, prevents wear and extends the life of engine.

Functions of Engine Oil:

• Friction Reduction: Moving parts inside the engine are in constant contact. Engine oil reduces friction and wear by forming a film layer between these parts.
• Cooling: Engine oil prevents overheating by dissipating the heat generated during engine operation.
• Cleaning: It ensures efficient operation for the engine by cleaning and removing dirt, soot and deposits inside the engine.
• Corrosion Prevention: It extends the life of the engine by preventing rust and oxidation that may occur in engine.
• Providing Sealing: It prevents loss of efficiency by providing a seal between the piston and cylinder walls.

Important Factors in Engine Oil Selection

Engine oil selection is critical for engine’s health and performance. Using wrong oil can accelerate engine wear and increase fuel consumption. Here are the important factors to consider when choosing engine oil:

1. Engine Manufacturers (OEMs) Recommendations

Engine oil specifications mentioned in the vehicle owner manual must be observed. The manufacturer's (OEM) recommended viscosity value (SAE classification), API and ACEA standards must be checked.

2. Viscosity Value of Engine Oil (SAE Classification)

Viscosity indicates fluidity of the oil against temperature changes. The viscosity classes determined by SAE (Society of Automotive Engineers) are as follows:

Example: 5W-30

• 5W: Indicates fluidity of the oil at low temperature (lower value means better performance in cold weather).
• 30: Indicates thickness of the oil at high temperature.

3. Engine Oil Types

Engine oil is divided into three categories according to their base oil content:

• Mineral Oils: Suitable for older generation engines, need to be changed more frequently.
• Synthetic Oils: Provides better performance and protection, long life.
• Semi-Synthetic Oils: It is a mixture of mineral and synthetic oils, offers medium level protection and price advantage.

4. API (American Petroleum Institute) Classification

API classification indicates the quality and application of the engine oil. Different API codes are used for petrol and diesel engines:

• For petrol engines: Starts with the letter ‘S’ (for example, API SN, API SP).
• For diesel engines: Starts with the letter ‘C’ (for example, API CK-4, API CI-4).
• Using the most current and advanced API classification will protect engine better.

5. ACEA (European Automobile Manufacturers Association) Standards

• A/B Class: For passenger cars and light commercial vehicles (e.g. ACEA A3/B4).
• C Class: Low ash oils for modern vehicles using DPF (Diesel Particulate Filter) (e.g. ACEA C3).
• E class: Used for heavy-duty diesel engines (e.g. ACEA E9).

6. Oil Selection According to Vehicle Type

• Gasoline vehicles: Generally, API SN or SP grade, low viscosity oils are suitable.
• Diesel vehicles: API CK-4 or CI-4 class oils suitable for fuel containing high sulphur should be preferred.
• Turbo engines: Fully synthetic oils resistant to high temperatures should be used.
• LPG vehicles: Special oils with low phosphorus and sulphur content are recommended.

7. Fuel Economy and Environment Friendly Oils

Modern synthetic oils can reduce fuel consumption by providing lower friction. ‘Low SAPS’ (low sulphate ash, phosphorus and sulphur content) oils are less harmful to the environment and compatible with particulate filters.

8. Selection According to Oil Change Frequency

• If you change oil frequently: Mineral or semi-synthetic oils may be preferred.
• If you want to change at longer periods: Full synthetic oils provide better protection.
• However, the best guidance should be following up vehicle owners’ manual requirements.

Summary

When choosing engine oil, oils meet the viscosity and quality standards in accordance with the manufacturer's recommendations should be preferred. The conditions of use of the vehicle, climate and engine type should also be taken into consideration.

When to Change Engine Oil?

Engine oil should be changed at regular intervals to ensure healthy engine operation. The oil change period depends on type of oil used, driving conditions of vehicle and type of engines.

General Oil Change Intervals

• Mineral Oils 5,000 - 7,500 km or every 6 months
• Semi-synthetic Oils 7,500 - 10,000 km or every 6-12 months
• Synthetic Oils 10,000 - 15,000 km or every 12 months

Important Note: The best approach is to follow the replacement interval specified in your vehicle's owner's manual.

Factors Affecting Oil Change Period

Engine oil change period may vary depending on the use of the vehicle and environmental conditions:

• Heavy traffic and frequent stop-start → Requires more frequent changes.
• Short-distance driving → Oil may become contaminated more quickly because the engine is not fully warmed up.
• Extremely hot or cold weather conditions → May affect viscosity of the oil and reduce its performance.
• Carrying heavy loads or towing a trailer → Causes engine work harder and shortens the life of the oil.

Signs for Engine Oil Change

Following signs may indicate that your engine oil needs changing:

• Engine Oil Warning Light: If the oil lamp is illuminated on the dashboard, you should have oil checked.
• Oil Colour Change: New engine oil is golden yellow in colour. If it has become dark brown or black, it is time to change it.
• Increased Engine Noise: If engine runs noisier than normal, oil may not provide enough protection.
• Increased Fuel Consumption: Old oil can increase fuel consumption by reducing the efficiency of the engine.
• Increased Exhaust Smoke: Black or blue coloured smoke may indicate that the oil is burnt or dirty.

What Should Be Considered During Oil Change?

• Use the oil type recommended by manufacturer(OEM).
• Oil filter must be replaced at every oil change.
• Check the oil level regularly.
• Check for leaks under the engine during the oil change.

Regular oil changes prolong engine life, reduce fuel consumption and improve vehicle performance.