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Maintenance Minute: They Make 0W Oil?

We're familiar with 10W-30 or 5W-20 oil grades and so on.
Did you know oil companies also formulate 0W grade oils? But unless you are starting an engine in -45° F. weather, you won’t see it for sale in your area.
The fact that an 0W oil grade exists provides an opportunity to explain the “pour point” rating of engine oil.
Let's take a typical winter grade oil like 5W-40, for example.
5W (the “W” represents the oil’s winter grade . . .not its weight) means that oil has a pour point down to -40° F. Thus, the pour point of that grade of oil is 5°F. above the point at which cold oil shows no movement on its surface for five seconds when it is inclined.
The base oil in 0W-40 is the same as 5W-40 . . . but the pour point of 0W-rated engine oil has been formulated to be lower because of its chemical formulation.
If you are confused by the term pour point vs. pumping temperature (commonly referred to by manufacturers), understand that pumping temperature is the temperature at which the oil will pump around the engine and maintain adequate oil pressure. This is typically 20°F. above the pour point. Thus, pumping temperature is 25°F. above the temperature point at which engine oil basically becomes a gel.
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