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What Is Oil Viscosity?

Understanding Properties of Motor Oil

When you get an oil change, whether you do it yourself or have someone else do it, you likely know that you need to get the right type of oil. Different motor oils have ratings such as 5W-30. This represents the oil viscosity. A lot of drivers don’t really understand what this means. Understanding it can help you make better decisions for your vehicle.

What Is Viscosity?

In the simplest terms, viscosity is the “thickness” of the oil. More accurately, it is a measure of how much the oil resists deforming. For example, a more viscous oil will pour less easily than a less viscous one. In other terms, molasses is more viscous than water.

The ratings on motor oil are for specific temperatures. Heat makes fluids more viscous. So, the temperature of the rated viscosity needs to be standardized and included in the rating.

Reading the Rating

Motor oil usually carries a rating of a number and a letter followed by a two-digit number. As mentioned above, an example of this is 5W-30. The two numbers are the viscosity ratings when the engine is cold and when it is hot. The letter indicates the standardized exterior temperature. In this case, the oil has a viscosity rating of five at winter temperatures and 30 when heated by the engine. A hot engine is 100 degrees Celsius according to the rating system standards.

Most commonly-used motor oils use the “W” winter temperature rating standard. So, they may actually be more viscous than the rating says due to higher environmental temperatures.

Why This Matters

You may think that this is the sort of thing only mechanics and engineers need to know about. While it is true that you could simply follow instructions in your owner’s manual without understanding the meaning, knowing what the viscosity rating is can be helpful. In general, you should follow your manual’s instructions. However, in some cases, you may be driving in relatively extreme temperatures and need to adjust your oil. Knowing what viscosity means can help you make better choices.

Get an Oil Change

If you need an oil change or other automotive services, come to our West Miramar Automotive & Transmission location at 5726 Miramar Rd any of our other convenient locations. You can also schedule an appointment online to get started.

Written by West Automotive Group