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Engine Oil | A Comprehensive Guide | Everything You Need To Know

It is often said that its easy to buy a vehicle than to maintain it. Many people buy the vehicle but are too lazy to maintain it. A person who loves his/her vehicle knows how important is to correctly maintain their vehicle. One of the most ignored components of maintenance is engine oil. It is known by different names, motor oil, lube oil, lubricant.


History of The Fluid

The first lube oil was developed by an American John Ellis on 6th September 1866. He realized the lubricating properties of crude oil. John first successfully tried the engine oil in a steam engine. He made a discovery developing an oil out of crude oil which effectively lubricated at high temperatures.

Purpose of Lube Oil

A vehicle’s engine is the most complicated component. A lot of research and development goes into the manufacturing of an engine. The calculations involved in making are very complex and precise. So it is very important to keep the complex parts inside the engine working perfectly. This is where the oil comes in.

Lube oil is the blood for our vehicle’s heart which plays many important roles. So it is necessary to note which engine lubricant we put in our vehicles.


  1. Lubricates Moving part

    • Any moving part be it a human body or any machine it requires lubrication.
    • Preventing friction is the most important use and feature for the engine oil. The Friction between the moving parts of the engine. These include the piston and the cylinder wall, crankshaft, the main bearings, valves in the head to name a few.
    • Lubricating all the moving parts inside the engine prevent these parts from grinding with each other. Inturn increasing the life and refinement of the engine.
    • Proper maintenance and regular lube changes prevent costly repair of the engine.
    • A good quality oil lets it run freely without any efforts what so ever. A good fuel economy, good refinement, and ultimate performance are all side products.
  2. Help reduce combustion byproducts

    • The fuel enters the combustion chamber from the injectors or the intake valve. In spite of controlled combustion, it produced byproducts.
    • These byproducts include the COx (Carbon Oxides), NOx (Nitrogen Oxides), SOx (Sulphur Oxides) and many more.
    • Engine oil prevents the depositing of the carbon on the cylinder walls. This is due to the high viscosity it evenly circulated the by-products.
    • The oil also reduces the piston’s effort and results in a better combustion process.
      Note: This is why the oil turns black after use. 
  3. Dissipates heat away from the combustion chamber

    • Due to many processes like combustion and friction the engine dissipates heat.
    • Either the coolant channels the heat out of the engine or the engine oil.
    • The oil gathers the heat from the combustion chamber and as it circulates it dissipates all the heat out of the chamber.
    • Circulating lubricant inside the chamber helps better channel the heat out of the engine.
    • This results in a better and efficient combustion process.
  4. Minimizes oxidation inside the engine

    • The whole concept of the engine is based on combustion and combustion without oxygen is not possible.
    • It is highly likely that the engine will be a victim of oxidation.
    • In Oxidation, the engine experiences corrosion inside.
    • The oxygen from the environment either enters through the inlet valve or through the water content in the coolant.
    • Oil slows the oxidating down to a large extent.
    • The oil inside the engine forms a wall on the outer layer of the cylinder not letting it get in contact with oxygen.

Also Read: Oil Thy Engine

Having so many purposes the engine oil goes through a rigorous test and developments before getting into your car. So one should pour the recommended engine oil inside the car for optimum life and performance.

Rating | SAE


SAE stands for Society of Automotive Engineers. It is the organization that decides the regulations and rating for automotive parts. Similarly, the engine oil has different ratings depending upon the viscosity, density, running temperature and many other physical attributes.

One likely will get confused about which grade or rating of oil to buy.

Viscosity: It is the state of being thick, sticky, and semi-fluid inconsistency, due to internal friction.

Density: It is a measurement that compares the amount of matter an object has to its volume.

Running Temperature: The maximum temperature at which engine oil works efficiently.

Oil Grading


Monograde rating: SAE 40 or SAE10W (example) 

  • This type has just one rating instead of two. There exist two types of monograde oils. ‘W’ grade oils for running in low temperatures and conventional grading to run at high temperatures.
  • They are designed to run on the fairly low spectrum of temperatures. Monograde oil is usually used in transmission.
  • For example, SAE5W is low viscous oil. This engine oil is capable of running at low temperatures. As the temperature increase, it becomes even less viscous. Hence losing the lubricating property.
  • On the other hand, SAE40 is a highly viscous oil. This oil is capable of running at temperatures of about 40° celsius. The oil might not function properly when running on lower temperatures.

Multigrade rating: 10W40 (example)

  • The oils having many grades and wider running temperatures are multi-grade oils.
  • The two numbers on either side of the rating suggest the viscosity rating. The lower the viscosity rating the oil is thin at low temperatures while cold starts.
  • 10 in the above example shows that it is tested at a low temperature and has a viscosity rating of 10. On the contrary, if the number is 5 the engine oil is even less viscous.
  • This makes the engine oil to flow easily during cold starts.
  • On the opposite end, 40 rating is the maximum limit of the engine oil tested under 212°F. A 40 rated engine oil has high viscosity under high running temperatures.
For further clarification:

During Cold start

  • 5w-40 will flow better than a 10w-40.
  • 10w-50 will flow better than a 15w-50
  • 5w-40 is the same as a 5w-30

At Operating Temperatures

  • 10w-50 is thicker than a 10w-40.
  • 15w-50 is thicker than a 5w-40
  • 0w-40 is the same as a 10w-4

As we now know what engine oil is for and how it differs with different gradings lets look at its different types.

Also Read: 7 Questions You Should Ask About Your Car Engine Oil

Types of Engine Oils

Over the years the automobile industry has come far in terms of technology. Components are getting more and more refined. These are getting more efficient in their work. There are 3 categories of the engine lube depending upon the vehicle and make.

  • Mineral Engine Oil
  • Synthetic Blend Engine Oil
  • Fully Synthetic Oil

Mineral Engine Oil


  • This type of oil is the oldest amongst the three. Mineral engine oil first ran in 1908 in the Ford Model T’s engine. After that, the engine oil tech has come a really long way. The amount of research went into the development is tremendous.
  • Conventional mineral oil only provides basic friction protection to the engine. Most of the new vehicles come with mineral oil from the factory.
  • This is to efficiently do the run-in period of the vehicle. During the run-in period, the engine is not stressed for the first 1000-1500kms depending upon the engine.
  • During this period it is recommended to run the engine on mineral oil.
  • Conventional oil is cheaper than other engine oils.
  • The engine oil replacement is very often in the vehicles running on this engine oil.
Engine Oil Grade (Mineral Oil) Characteristics
10W-40 Basic engine wear protection
15W-40 Oil changes are more often

Synthetic Blend or Semi-Synthetic


  • The middle ground for the engine oil is a semisynthetic one.
  • It has many benefits over mineral oils as it consists both, synthetic oil as well as mineral oil.
  • Semi-synthetic oil has better protection to wear than conventional mineral oil.
  • This oil offers a tad better protection during cold starts.’
  • Though Fully synthetic oil is better, it is the price that forces us to think once again.
  • It also acts as a mediocre when upgrading the engine oil from mineral oil to fully synthetic oil.
  • Comparing the oil and the synthetic blend, the new one offers many kilometres before oil changes.
Engine Oil Grade (Mineral Oil) Characteristics
5W-30 Better protection than the mineral oil
10W-40 Good protection during cold starts
15W-40 Increases the oil change time period 

Fully Synthetic Engine Oil


  • The latest and the greatest technology in this fluid is the fully synthetic engine oil.
  • Fully synthetic oil is produced using synthetic materials in labs by specialized chemists. This gives the engine oil the best industry has to offer.
  • These oils provide top-notch fuel economy, power, and refinement.
  • Since these oils are produced with controlled blends they can be used to bring out the maximum effort.
  • It also helps in effortless cold starts.
  • Since these are resilient against degradation, oil changes are even less than semi-synthetic ones somewhere after 10,000kms to 15,000 kms.
Engine Oil Grade (Mineral Oil) Characteristics
0W-30 Increased fuel economy
0W-40 The enhanced power output of the engine
5W-40 Seemless engine cold starts

Which type to use?

It gets even more confusing now which engine oil to use. But the car manufacturers have got it covered. They prescribe a specific grade of oil that should be used. Considering that the customers don’t require to be confused unless they want something specific with their rides.

After all, it’s not just oil it’s liquid engineering.

Also Read: Engine Oil Grades Explained | Know Your Car Engine Oil

Utkarsh Bhardwaj
Utkarsh Bhardwaj
Technical Content Strategist at GoMechanic | Big Time Petrolhead with the passion for building cars and driving those beauties.


  1. Thanks for sharing this information. Engine oil is very important when it comes to automobiles. Gs Caltex is a brand that focuses mainly on engine oil and vehicle oil.

  2. Thanks for sharing this useful information with us, this is really meaningful to us for selecting the accurate things for our products in a right manner.


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