Importance of Oil Viscosity Chart for Car Owners

An understanding of the Oil Viscosity Chart is must for all drivers before buying the can of Motor oil. This will help you in choosing the perfect oil for your car and increase its life.


SAE (Society of Automotive Engineers) has designated the numbers for Motor Oil like :

  • SAE 5W
  • SAE 10W
  • SAE 20W
  • SAE 20
  • SAE 30
  • SAE 40
  • SAE 50

The above Oils are known as Single grade oils. The downfall of using single grade oil is constant changing of the oil. For example, SAE 5W will work perfectly fine for cold starting the car but will not offer sufficient engine protection at higher temperature. So either you have to use multi grade oil or change the oil in your depending upon the weather conditions. Keep in mind :

  • Viscosity is directly proportional to the SAE number. It means that higher the number, thicker the oil.
  • The W after the rating stands for the Winter Grade. It means that these oils are tested at 0 degree Fahrenheit. These oils are suited for cold start.
  • The Rating like SAE 30 (without w) is tested at 210 degree Fahrenheit .These oils give better engine protection at higher temperature.

What is Multi grade Oil?
Multi grade Oil combines the properties of two single grade oils. For example, SAE 10W-30 means that it combines the cold starting ability of SAE 10W oil with the engine protection ability of SAE 30 at higher temperatures. The Multi Grade Oil gets its properties from additives. These additives fill the spaces caused by the expansion of Oil at higher temperature.

Now if you are using SAE 10W 30 in your car, you know

  • It is ok to start your car at even minus ten degree Fahrenheit.
  • It will protect your engine from wear and tear till 30 degree Fahrenheit.

Should i use Multi grade or Single Grade for my Car
It all depends upon the weather condition that you live in. If you are living in Alabama, Georgia or Florida, you can use the single grade oil as the temperature remains constant over the year. Multi grade Oil (SAE 10W – 30) is a good choice if you live in other parts of USA as the temperature varies rapidly.

Some points about multi grade oil

  • You can use the same oil under all weather conditions.
  • Protection over the specified temperature range.
  • It is costlier than single grade oil.

Two points to know before buying Motor Oil

  • When you start the car, you want your motor oil to reach the engine as soon as possible to reduce the friction between engine parts. It means that at the time of starting the engine oil should be thin for fast travelling.
  • But when your engine is running, you want your motor oil to be thick to provide better lubrication. But the viscosity reduces with the rise in temperature leading to the expansion of the Oil. So additives are added to increase the thickness at higher temperature.

Check API service rating before buying your Motor Oil
Look at the top of your motor oil can for “SE” rating .SE rating means that your motor oil has all the additives recommended by the American Petroleum Institute.

Points to remember

  • Always use motor oil recommended by your manufacturer.
  • Check top of oil can for ratings.
  • Always buy a branded one.
  • Keep the weather condition in your mind when buying oil.

Multi grade oil is the recommended over single grade.