Ultimate Engine Oil Buying Guide

You are driving a car, maybe going to your office, for a vacation, for a business meeting or heading to a friend. Suddenly a light pops up on the dashboard, which indicates low engine oil. You rush to the nearest gas station to find suitable engine oil for your car. There you see hundreds of engine oils on the shelf and you have no idea which one you should choose for your vehicle. We have all faced this situation at some point. Most people are reluctant to choose engine oils on their own, because of less awareness and lack of expertise. Going to a mechanic may cost a lot. You do not have to be a professional, nor do you need one to pick the suitable oil for your car's engine. Let's walk through simple steps to get you the right motor oil for your vehicle.

In this article:

Why Are There So Many Engine Oils?

Each engine oil in the market is manufactured for a specific type of car or any specific brand. In simple words, every brand designs an engine with different specifications, for different situations, different climates, and different purposes. After manufacturing, hundreds of tests have been conducted for choosing the perfect oil for that engine. These oils are different from one another based on their viscosity grades, types, and usage. Before choosing the right oil, keep in mind-

  • The vehicle type you use- high performance, heavy-duty, etc.
  • Purpose- Commercial, personal, etc.
  • Usage- Distance, Terrain, etc.

Factors To Consider While Choosing The Right Oil

Take A Look At The Manufacturer's Manual

After conducting multiple tests on a particular engine, the engine manufacturer recommends the best suitable oil for that engine. As per the needs and requirements of the vehicle, manufacturers include additives, decrease or increase the oil's viscosity, and suggest between conventional, synthetic, or blend oil. This oil benefits your engine in multiple ways. It enhances engine life by reducing wear, lubricating properly to help in starting the engine and maintaining suitable viscosity at operating temperature. 

Though it is advisable to use the recommended oil for your car’s engine if you still feel the need to choose otherwise, here are some points to make an informed choice.

Different Viscosity Grades

The viscosity of a fluid is its resistance to flow. Viscosity changes with temperature. Engine oils are graded in _ _W_ _ format. W represents winter. The digits before ‘W’ are the oil viscosity when it is cold. It tells you how thick the oil is when you are starting your car after it stays outside on a cold winter night. It varies from 0 to 25 by the steps of 5. For example, 25W oil is more viscous and thicker than 0W oil at a low temperature of -10 degrees. The most common oil grades for modern vehicles are from 0W to 15W.

Pro Tip- A rule of thumb is that if you subtract (-35) from the viscosity grade, you will get the minimum temperature that an oil can tolerate. For example, If you have 5W motor oil, it can tolerate low temperatures up to -30 degrees.

More than 80% of the engine wear occurs during the cold start, because of the delay in lubrication. It takes a small fraction of the time for oil pressure to build up and lubricates all the parts of the engine. The time taken by 0W grade oil to reach the optimal pressure and lubricate the components is less in comparison to other grades. The use of lower grades in this situation will help to extend the life of the car's engine.

The digits after ‘W’ are called the higher temperature grade and can vary from 8 to 60. These digits show the different viscosity of the engine oil at the car's operating temperature. Lower numbers indicate thinner oil or lower viscosity and higher numbers indicate thicker oil or higher viscosity. It means W60 is far more viscous and thicker than W8 at an operating temperature of 90 degrees. The most common grades for modern vehicles are from 16 to 40. In order to enhance the fuel economy of cars, many car brands began to use motor oils with lower viscosity grades. If the oil is less viscous and thinner, it requires less energy to pump and push it through the engine block and requires less fuel.

Pro Tip- It is recommended to opt for the suggested high-temperature grade by the owner's manual as reducing this gradient can cause significant damage to the engine. 

It is better to choose 5W-30 over 10W-30 if you use your vehicle for short distances, as your car’s engine is exposed to cold conditions the majority of the time. Also, it will enhance the economy of your car because 5W-30 will flow smoothly and requires less power and less fuel than 10W-30 in cold conditions.

Performance Level

Every car engine oil is designed with hundreds of specifications and technical details.  Two broad international specifications we need to look at, as it covers the majority of minor specifications. These two international specifications are ACEA and API.

ACEA (European Automobile Manufacturers' Association)- This association unites Europe's 16 major car, truck, van, and bus makers to set tested standards for oil manufacturers of European cars.

API (American Petroleum Institute)- This association certifies those oil manufacturers who match the set tested standards for American vehicles.

So when you see the above acronyms on the engine oil bottle, rest assured that it has been certified by experts. 

Pro Tip- Always choose the right oil from a brand that displays the starburst symbol that indicates the oil has been tested by American Petroleum Institute (API). 

Types Of Engine Oil

Engine oils can be classified into five categories based on their manufacturing processes. These are-

Full Synthetic Oil - This oil flows better at low temperatures and reaches peak viscosity at high temperatures. This oil is mainly formulated in a laboratory and hence highly purified. That is why it also costs more. It is considered suitable for heavy-duty vehicles.

Semi-synthetic Oil - This oil is a blend of organic and synthetic oil. As it offers protection against high temperatures and heavier engine loads, it is suitable for SUVs.

High-Mileage Oil - This oil is formulated using additives to the base oil to ensure high mileage for old cars to sustain longer.

Conventional Oil - These oils are created by adding the least additives to the base oil hence, they have the lowest cost among all. These oils are likely to contain impurities and can cause sludge build-up. They are not suitable for high-performance vehicles. Easily available at every auto shop.

Premium Conventional Oil - These oils are available in multiple viscosities to cover a large group of vehicles. These are suitable for light-duty vehicles.

These tips will be very handy when purchasing engine oil. Enjoy!


Articles and Guides that are written with the help of mechanics to ensure you have all the knowledge you need to make the correct purchase here at PartsAvatar.

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Yes, you can put engine oil in your car by yourself. Make sure to park your car on an even surface to pour the correct amount. Always use a funnel to avoid spills on other parts.

It is advisable to buy the recommended engine oil by the car manufacturer’s manual. This will extend the life of your car’s engine. If you want to buy otherwise, you should consider factors like driving conditions, hours of driving per day, types of vehicle you own, the viscosity of engine oil etc.

First, make sure your car is parked on level ground and the engine is cold. Open the car’s hood and find the dipstick. Pull the dipstick out and wipe it off from the end to remove any oil. Then put the dipstick in and then slowly pull out. Every stick has some indications like L&H (Low & High), Min and Max, etc. See the oil end. If it lies in between these indications, the engine oil level is fine.

Have your oil changed every 8000 to 11000 km or 6 to 8 months, whichever comes first. If your car requires full-synthetic oil, it could even go as far as 15,000 miles between services. Such intervals should be reduced by half under severe driving conditions.

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John Framigllia
Technical Writer
Our technical writer is known for simplifying automotive parts and services. Intuitive with various vehicles and manufacturers, he knows how to simplify complicated problems.