Engine Oil Viscosity Rating: What It Is & Why It’s Important

Your car’s engine oil is literally the lifeblood of it’s engine. Without it, your car wouldn’t get very far before the engine quit working. The oil acts as a barrier to keep metal parts from rubbing together, and as a coolant to help keep pistons and other parts from getting too hot.

Using the right oil makes a big difference in how long your car’s engine lasts, too! One of the things you’ll need to keep an eye out for is the engine oil viscosity.

What Is Engine Oil Viscosity?

Engine oil viscosity refers to how easily oil pours at a specified temperature. 0w20, 5w20, and 5w30 are all examples of oil viscosity ratings. Motor oil grades are defined from an industry specification known as SAE (Society of Automotive Engineers) J300.

Let’s use 0w20 as an example. The “0” represents the viscosity when cold. The better the oil performs at lower temperatures, the lower the number before the W. The “20” portion of the 0W-20 grade relates to how the oil flows through the engine at higher temperatures.

What Viscosity Is Best For My Car?

We recommend following the manufacturer’s recommendations. Your owner’s manual should have an oil viscosity chart that will tell you what viscosity you should be putting in your car, based on your climate. Like this:

Modern vehicles are designed to use a thinner oil in both winter and summer. Engines are very sophisticated, using cam phasers and variable valve timing, which change the engine timing for power and economy according to how you drive. These phasers require lightweight oils to pass through the tiny orifices when the oil is cold to work properly.

What About Synthetic vs. Conventional Oils?

Especially in the valley, you’ll want to use a good synthetic oil as much as possible. The reasons are:

  • Better hot and cold temperature performance, so you enjoy worry-free start-ups in freezing weather, and less burn-off when it’s scorching.
  • Enhanced resistance to motor oil breakdown due to oxidation and extreme heat.
  • Improved fuel economy, so you can save money on gas!
  • Reduced engine drag for better horsepower.
  • Less engine sludge, thanks to fewer impurities.
  • Greater engine wear protection.
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