Oil Viscosity Explained

What You Need to Know

If you have ever tried to purchase motor oil, you know that there are many kinds to choose from. Not just any motor oil off the shelf will be the right one for your vehicle! You need one with the right viscosity — one that’s not too thick to flow through the engine effectively! Viscosity can be difficult to understand, with all the different numbers and letters used to provide information. That’s why Jeff’s Auto Repair in Seattle, Washington is taking a moment to explain viscosity and how it’s labeled. This summary can help you make the right selection for your vehicle!

Resistance to Flow

Viscosity refers to a fluid’s resistance to flow. A thick oil (think thick like syrup) has a high resistance to flow and a high viscosity. Something with low viscosity, like water, flows quickly and easily.

Multiple Grades

Most oils have a range of viscosity grades, which is where some vehicle owners can get easily confused. There won’t be just one number on the bottle to tell you what you need to know. The reason for this is because viscosity can change at different temperatures.

You want to make sure the oil you put into your car will stay within an appropriate viscosity range at extreme high and low temperatures. This means that where you live, and how cold or hot it gets there, has an impact on the kind of oil you get!

Viscosity grades use a number followed by a “W” for winter to indicate the oil’s rating at low temperatures. The lower this number is, the better it will flow in cold temperatures, where oil is known to thicken up. The next number indicates the viscosity at high temperatures, where oil is known to thin out.


These numbers can help you find an oil that won’t thin out in the heat or thicken up the extreme cold, which means your engine will be protected through all weather conditions! Work with your local auto repair experts to find the right choice for your specific vehicle. Jeff’s Auto Repair in Seattle, Washington takes manufacturer recommendations into account to find appropriate motor oils for all vehicles that visit our shop.

Written by Jeff's Auto Repair

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