What is Engine Oil?

What is Engine Oil?

Engine oil, or motor oil, is designed to lubricate and protect internal combustion engines.

It comprises two main components: base stock (95%) and additives (5%).

The base stock, derived from petroleum, synthetic chemicals, or a mix, lubricates and removes heat.

Engine oils are rated by grade and viscosity, with multi-grade oils common for year-round use.

An image illustration of What is Engine Oil
What is Engine Oil
PHOTO Courtesy | Freepik

What is Engine Oil? Background

On September 6, 1866, John Ellis founded the Continuous Oil Refining Company in the U.S.

Originally exploring crude oil for healing, he shifted focus to its lubricating potential.

Driven by a quest for better steam engine lubrication, he successfully created a high-viscosity petroleum-based oil, addressing issues in the era’s engines that used inefficient blends.

This breakthrough, achieved by Dr. Ellis, meant better performance at high temperatures, reducing problems like valve blockages and cylinder corrosion.

Engine Oil Use

Engine oil lubricates and protects internal combustion engines in vehicles and machines.

It minimizes friction, reduces wear, and dissipates heat.

The oil’s additives clean the engine and prevent sludge.

It also acts as a cooling agent. Without enough oil, engines can suffer damage, including wear and engine seizure.

Non-Vehicle Motor Oils

Used in machines like portable generators, lawnmowers, snow blowers, chainsaws, and gardening equipment.

They include four-stroke oil for certain engines and two-stroke oil for others.

In small engines, two-stroke oil is sometimes mixed with gasoline, while larger engines may have an oil injection system.

The properties of these oils vary based on the specific needs of the equipment.

Environmental regulations, particularly in Europe, promote the use of ester-based two-stroke oil for leisure marine applications.

Motor Oil Properties

Motor oils are made from thick petroleum with additives to ensure proper lubrication.

Viscosity, flash point, TBN, and TAN are key properties, with the viscosity index indicating temperature-dependent changes.

Oil Change and Maintenance

Regular oil changes are essential to maintain engine health.

This involves draining old oil, replacing the filter, and adding fresh oil.

Over time, oil accumulates particles and degrades in viscosity and alkalinity, affecting lubrication and engine protection.

Manufacturers recommend specific oil grades, but factors like driving conditions and intervals also influence when to change oil.

Modern cars may have longer intervals and quality synthetic oils offer stability.

Quick oil change shops may suggest shorter intervals, but following the vehicle manufacturer’s recommendations is key.

Adjusting Oil Viscosity

Engine users can adjust oil viscosity based on ambient temperature—thicker for summer and thinner for winter.

Lower-viscosity oils are common in newer vehicles, improving fuel efficiency.

The industry’s move towards lower viscosities led to the introduction of the SAE 16 viscosity rating in 2013.

Thus expanding options beyond the traditional “divisible by 10” system.

Industry Standards for Engine Lubricants

  • API Standards:
    • Evaluate oils against SJ, SL, SM, SN, SP, CH-4, CI-4, and more.
    • Set minimum performance levels.
  • API Service Classes:
    • Classify oils into S (spark ignition) and C (compression ignition).
    • Latest category: API SP for gasoline engines.
  • Diesel Engine Service Categories:
    • Include API CK-4, CJ-4, CI-4 PLUS, and more.
    • Introduce API FA-4 for enhanced fuel economy.
  • ILSAC Standards:
    • Establish standards like GF-4, GF-5, GF-6A, and GF-6B for gasoline engines.
    • GF-6B specifically for SAE 0W-16 viscosity oil.
  • ACEA Classifications:
    • Use stringent A3/B3, A3/B4, A5 classifications for European engines.
  • JASO Standards:
    • Define standards like T904-MA, T904-MA2 for four-stroke gasoline engines.
    • Address unique requirements for Japanese-origin petrol engines.
  • ASTM Challenges:
    • Report challenges in defining HTHS standards.
    • Kinematic viscosity is less relevant due to multigraded oil growth.

Environmental Impact

Used motor oil poses a severe environmental threat due to its toxic composition. Petroleum-based lubricants, common in motor oils, are harmful to the environment.

Over 40% of water pollution in the U.S. is attributed to used motor oil, mainly from improper disposal.

Disposing of used oil improperly affects soil productivity and contaminates water supplies, soil, and groundwater.

Engine Oil Packaging

Motor oil packaging has evolved from glass bottles and metal cans to plastic containers.

Commonly sold in one-quart bottles, larger sizes, and distributed in bulk to service centers, packaging has adapted to suit engine oil needs.

An image illustration of Engine Oil
Engine Oil
PHOT Courtesy | Freepik


Human ingestion of motor oil is dangerous and can lead to health issues.

Ingesting small amounts may cause digestive problems, while exposure to an open flame can result in ignition.

Skin contact with motor oil can lead to defatting, emphasizing the importance of proper handling.

What is Engine Oil? (FAQs)

1. What is engine oil?

It is a specialized lubricant crucial for internal combustion engines.

It minimizes friction, cools the engine, prevents corrosion, and cleans contaminants to ensure smooth engine operation and longevity.

2. Why is engine oil essential for a vehicle?

Engine oil is vital as it lubricates moving parts, reduces wear, and prevents overheating in a vehicle’s engine.

It ensures optimal performance, and efficient fuel combustion, and acts as a cleaning agent, removing debris.



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