Engine Oil Grades

Reading your engine oil grade & understanding what it means!

India is one of the top 10 vehicle manufacturing countries in the world. The vast demand in vehicles in the automobile industry and in agricultural vehicles only means there will be an enormous requirement of engine oils and lubricants. Production of high quality oils will be a priority for oil manufacturers. Understanding different grades and ratings of engine oils and lubricants is an essential part of the automotive industry.

Purpose of Engine Oil

The engine is one of the most complicated components of a vehicle. A lot of research and development goes into the design of an engine. So it is of utmost importance to keep the complex parts inside the engine working smoothly. Oil plays a crucial role here. So it is necessary to note which engine oil lubricant we use and the different purposes they have.

  • Lubrication: Engine oils have multiple purposes, one of the key functions of an engine/motor oil is lubrication. Preventing friction between the moving components is the most important use and feature for the engine oil. The piston, cylinder wall, crankshaft, the bearings and the valves in the head to name a few are the main components of an engine. Lubrication increases the life and refinement of the engine. Proper maintenance and regular engine oil changes prevent costly repairs. A good quality oil lets it run smoothly reducing wear and tear.
  • Regulation of internal temperatures: Due to many processes like combustion and friction the engine dissipates immense heat. The oil gathers the heat from the engine and as it circulates it dissipates and reduces all the heat out of the engine. Circulating lubricant inside the engine helps better channel the heat out of the engine. Running of engines at optimum temperatures results in a better and more efficient combustion process.
  • Help reduce combustion byproducts: Every engine has multiple components that are important for its function. In spite of it being a controlled combustion, it produces byproducts. These byproducts include Carbon Oxides, Sulphur Oxides, Nitrogen Oxides and many more. Engine oil prevents the depositing of the byproducts on the cylinder walls. Due to the high viscosity it evenly circulates the by-products. The oil also improves piston movement efficiency resulting in a better combustion process. Combustion byproducts are the number one reason the oil turns black after usage.
  • Minimizes oxidation and deposition: 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. Oil slows the oxidising down to a large extent. The engine oil inside the engine forms a wall on the outer layer of the cylinder thus reducing oxidation and deposition in the engine.

Types of Engine Oils

Over the years the automobile industry has come far in terms of refinement and technology. Such improvements have created a major surge in production of essential engine oils.

There are 3 categories of the engine oils depending upon the vehicle and make.

Mineral Engine Oil

  • Conventional mineral oil only renders basic friction protection to the engine. Most often newer vehicles coming from the factories are stocked with conventional mineral oil.
  • This is done specifically to ensure an efficient run-in period of the vehicle. Run-in period refers to the first few thousand kilometres of vehicle usage.
  • Conventional mineral oil is cheaper than other engine oils.
  • Mineral engine oil may not be appropriate for running engines in extreme temperatures.
  • The periodic replacement of oils is shortened in the vehicles running on this engine oil.

Synthetic Blend/ Semi Synthetic Engine Oil

  •  The middle blend for the engine oils is the semisynthetic one.
  • It is a blend that consists of both synthetic oil as well as mineral oil.
  • Semi-synthetic oil has better protection to engine wear and tear than conventional mineral oil.
  • Semi synthetic oils offer better protection during cold starts.
  • Compared to mineral oil, synthetic blend oils offer many kilometres before oil changes.

Fully Synthetic Oil 

  • Fully synthetic oil is produced using synthetic materials. This gives the engine oil the best the industry has to offer.
  • These oils provide admirable fuel economy, power, and refinement.
  • Fully-synthetic oils not only protect the engine from the wear and tear but also controls the combustion by-products of the engine.
  • It helps in effortless cold starts and high running temperatures.
  • Since these are efficient against breaking down oil changes are lesser compared to the semi-synthetic ones.

Engine oil grades and ratings

Different vehicles and different engines require different oils for their functionality.  Engines can vary not only by the size but also as to what fuel it uses for combustion. It is very important for us to understand what oils and lubricants are to be utilised based on the vehicles. The oils and lubricants are graded and rated for universal standardisation and for simpler understanding.


SAE stands for Society of Automotive Engineers. It is the organisation that governs and regulates ratings for automotive parts. Engine oils have different ratings depending upon multiple physical attributes. Buying the right grade or rated oil can often be confusing.

  • Viscosity: It is a measure of a fluid’s resistance to flow. It gives information about the internal friction of a moving fluid.
  • Density: It is a measurement of the amount of matter an object has to its volume.
  • Running Temperature: The maximum temperature at which engine oil works efficiently.


There are two types of grades when it comes to engine oil.

  1. Monograde Rating: SAE30 or SAE5W 
  • There are two types of monograde oils. ‘W’ grade oils are often used  for running in lower temperatures and conventional grade oils to run at high temperatures.
  • They are designed to function on a rather low spectrum of temperatures. Monograde oil is mainly used in transmission.
  • For example, SAE5W is low viscous oil. This engine oil is efficient at low temperatures. With an increase in temperature, it loses its viscosity. Hence losing the lubricating property.
  • On the other hand, SAE30 is a highly viscous oil. This oil is capable of running at temperatures of about 30° celsius. This oil may not be suitable when running engines at lower temperatures.
  1. Multigrade Rating: 15W30
  • The oils having multiple grades and wider range of engine running temperatures are multi-grade oils.
  • The numbers on either side of the letter suggests the viscosity rating.
  • 15 in the above example shows that it is tested at a low temperature and has a viscosity rating of 15.
  • On the opposite end, 30 rating is the maximum limit of the engine oil tested under 212°F. A 30 rated engine oil has high viscosity under high running temperatures.

Engine oils and lubricants are an integral fragment of the automotive industry. Having the right knowledge about what oils do and which lubricant may be right for your vehicle is as essential as buying the right vehicle. Using the right oils and lubricants for a particular vehicle will guarantee a smooth-running engine and increase the longevity of the vehicle substantially.

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