Engine Oil Weights and Viscosity

Written by Lee Wyatt (last updated May 27, 2010)

Some common questions that people have about basic automotive care have to do with engine oil weights and viscosity and what the terms mean. In the case of automotive oil these words are referring to the thickness of the oil.

Most engine oil used today is multi-grade oil, which means that the substance is designed to operate in a variety of different circumstances. You can find this information, from the Society of Automotive Engineers (SAE), on the side of all motor oil products. This classification is what most people refer to when they say "10 weight" or "30 weight" and refers to the classification on the side of the bottle or can that reads 10W40.

10W40 is known as the SAE oil viscosity grade. This is a multi-grade oil. The W is referring to winter and the oil's viscosity during the colder times of the year. This is determined from testing that the SAE conducts to determine the performance of petroleum products during cold weather operation, while also protecting the engine from operating at higher engine temperatures and loads. If you are in an area of the country, or world, that has a warmer climate on average, then you can probably use a single-grade oil.

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Lee Wyatt

Contributor of numerous Tips.Net articles, Lee Wyatt is quickly becoming a regular "Jack of all trades." He is currently an independent contractor specializing in writing and editing. Contact him today for all of your writing and editing needs! Click here to contact. ...

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