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What is the purpose of engine oil in my vehicle ?

Engine oil plays several significant roles in ensuring that all these work together efficiently to ensure your vehicle runs cooler and cleaner and gives the best performance. Your motor oil helps Provide proper lubrication: Reduces friction and wear that occurs when parts move against each other. Provide Cooling: Absorbs the heat produced in the engine combustion chambers and piston under-crown area, thus cooling the engine and helps to prevent overheating. Provide Sealing: For the space between the piston ring and the cylinder liner to prevent combustion pressure i.e. engine power from escaping. Provide Cleanliness: The detergent in the oil prevents waste matter resulting from combustion and impurities produced by oxidation from sticking to the engine interior, to keep it clean. Provide resistance to corrosion and rusting: The rust inhibitor in motor oil, neutralizes acids produced by combustion gases, preventing corrosion and rusting in the long run.

What are API & SAE standards with respect to Motor oil

The American Petroleum Institute (API) has established a classification system for the designation of gasoline and diesel engine oils, which reflects the quality, performance, and suitability of the oils for various engines. These classifications, or categories as sometimes referred, have no bearing on oil viscosity, whose limits are set by the Society of Automotive Engineers (SAE) and designated in SAE J300. Contrary to the belief of many, the SAE grade only defines oil viscosity and has absolutely nothing to do with oil quality. To specify engine oil, both the API service designation and the SAE viscosity grade are required.

What is Viscosity?

Viscosity is the most important property of a lubricant and engine oil. It is a measure of a fluids resistance to flow. High viscosity means high resistance to flow, low viscosity means low resistance. The thinner a liquid is the less sticky or viscous it is. The viscosity of a fluid is a measure of its resistance to gradual deformation by shear stress or tensile stress.

What are different classifications in engine oils ?

These classifications are arranged into two different groups, one for automotive gasoline engine service and the other is for commercial diesel engine service. The former is listed in “S” or “Service” categories and the latter is listed in “C” or “Commercial” categories.

What’s the difference between Mineral and Synthetic Engine Oil?

Mineral or Conventional Oil are produced with base oils refined from petroleum crude which has been pumped from the ground to which chemicals (additives) are added to meet a performance standard

A synthetic or a synthesized material produced by combining or building individual units into a unified entity. These oils are man-made and tailored to have a controlled molecular structure with predictable properties.

What will happen to my engine if I don’t change oil?

All Engines work through by burning fuels such as gasoline or diesel. As a result, non-combustible by-products like residual gases, soot & sludge are produced. Engine oil captures and prevents these impurities from coagulating inside the engine and thus works to keep your engines clean but as it does this your engine-oil’s effectiveness diminishes over a period. The effects of combustion heat and oxygen in the air can also cause engine oil itself to deteriorate, and therefore it is essential that the oil be replaced after a period of use in your vehicle.

How do I read an oil specs? What does 5W-20 stands for?

As oils heat up during the running, they generally get thinner. Single grade oil tends to get too thin when hot. Therefore to prevent the base oil from getting too thin when it gets hot, the engine oils have different grades/ specs. The number before the ‘W’ is the ‘cold’ viscosity rating of the oil, and the number after the ‘W’ is the ‘hot’ viscosity rating. E.g. 5W-20 oil will behave like a 5-rated single grade oil when cold, but doesn’t get thin any more than a 40-rated single grade oil when hot. The lower the ‘winter’ number – W”, the easier the engine will turn over when starting in cold conditions.

Is it okay to use 5W30 in my vehicle where-as the owner’s manual mentions 5W20?


Manufactures suggest 5W20 to maximize fuel economy and performance for certain engines. When you choose 5W30 type it may cause a slight decrease in fuel economy. For the best performance in different conditions Veedol suggest to follow the oil viscosity and maintenance as per the vehicle owner’s manual.

When do I use mono-grade and multi-grade oil in my vehicle?


Mono grade oil is not recommended for use in an engine that requires a multi-grade viscosity. Mono grade are generally recommended for smaller engines and applications or older engines that were made prior to multi grade viscosity oils were introduced.

Can I use gasoline engine oil in a diesel car and vice-versa?

Generally Gasoline engines and diesel engines run on different fuel and they have different characteristics and therefore the performance requirements of engine oils must also vary accordingly.

I am not sure whether to use thicker or thin oil is best for my engine?

Depending on the conditions / weather thicker oil can be used to fill in wear gaps which must have developed over the years. However, Veedol re commendation is to always use the motor oil viscosity mentioned in your owner’s manual.