Understanding Oil Viscosity Numbers

Oil Viscosity Numbers


Few car fluids and chemicals are as important as engine oil. This essential lubricant keeps your engine running at high speeds without causing undue wear and tear on high-performance parts. However, it can be difficult to choose the right oil for your vehicle. Even when you discover the correct oil weight, all the different options can be confusing. Here is a helpful guide to understand why so many different oil types exist. 

What Is Oil Viscosity? 

Your oil viscosity, or oil weight, is determined by the ideal running temperature of your vehicle. Whether you use standard options, like 5W-20 or 10W-30, or more specialized oils, you need to choose the exact oil recommended for your engine.

Motor oil is given two viscosity ratings: hot and cold. The first number in your oil weight is followed by a W, which stands for winter. This number is the viscosity rating when your oil is at zero degrees Fahrenheit. The second number is the viscosity of the oil when your car’s engine is running and at high temperatures.

Why are these measurements important? Oil needs to be thick enough to properly lubricate your engine’s moving parts, while also being thin enough to properly flow throughout your engine.

The fine balance between the two is part of why there are so many types of oils. The other reason is that different engines run at different temperatures, so they require different types of oil. The latest hybrid SUV requires very different oil than a classic truck. Choosing a higher or lower number may seem like an upgrade, but could actually damage your engine by providing improper levels of lubrication. 

The Difference Between Synthetic and Conventional Oil 

Now that you understand the importance of the correct oil weight, you need to choose the type of oil that works best with your vehicle. Motor oil comes in three basic categories, as well as several highly specialized additional categories. The basic categories of motor oil are:

  • Conventional oil
  • Synthetic blend oil
  • Fully synthetic oil

You can also find high-mileage oil, high-tech engine oil and off-road oil. Basically, synthetic oil is used in high-tech engines that require strict specifications, while conventional oil is common in all other vehicles. A synthetic blend is an in-between option that offers some of the high temperature protection of synthetic while still balancing the viscosity and affordability of conventional oil. 

Before you shop for the best synthetic engine oil, remember that these oils are highly specialized. Don’t try to upgrade your vehicle to full synthetic oil if it isn’t recommended by the manufacturer. 

Choosing the Right Oil and Oil Filter 

Your engine deserves the best. However, even more expensive oils can damage your vehicle if it isn’t the correct weight and oil type. When shopping for motor oil and considering what oil filter do I need, choose the exact oil and filter recommended for your vehicle. Ask your local auto store for the correct oil viscosity for your vehicle and shop for the best brands for improved performance and efficient lubrication of your engine.

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