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OUR BLOG

06/16/2015
According to the Society of Tribologists and Lubrication Engineers (STLE), viscosity is the most important property of fluid lubricants. So how does it translate to the SAE viscosity rating on your motor oil bottle? AMSOIL is here to help translate!

The flow formula

Viscosity is the oil's resistance to flow or the oil's speed when measured by a viscometer device. The thicker, or heavier, the oil is (higher viscosity), the slower it will flow through. Kinematic (kV) and absolute (cSt) are oil viscosity measurements. These measurements are much easier to understand as SAE viscosity numbers on your motor oil bottle.

Why 5W-30 does not equal SAE 30

A "W" in a viscosity rating equates to the oil viscosity being tested at a colder temperature. Without the "W", the tests are at 210°F/100°C. This temperature is considered to be the approximate engine operating temperature.

Oil and your engine

5W-30 at the normal engine operating temperature (210°F/100°C) is the same viscosity as SAE 30 motor oil. The difference occurs when the viscosity is put to the test at colder temperatures. 5W-30 performs like an SAE 5 motor oil would perform at the cold temperature; however, it still has the SAE 30 viscosity at 210°F/100°C. This difference allows  the engine to get oil faster when started cold versus running the engine until it "warms up". The faster oil flows cold equates to less dry running time and less engine wear.

Tests do vary“W” 

ratings are tested with a different temperature system than SAE viscosity ratings. When determining non-winter grade viscosity a viscometer is used and the oil flows at normal engine temperatures while timed. SAE viscosity is determined by using a table based on different ranges. Heavier viscosity oils will take longer to flow through and, therefore, end up in the higher number ranges (like SAE 50). Lighter oil flows through faster and ends up within the lower range of numbers (like SAE 10).When it comes to motor oil for your vehicle, numbers matter. 

When it comes to finding high-quality synthetic motor oils, there's only one choice- AMSOIL. Call AMSOIL The First in Synthetics® at 863-698-1150 and get the right synthetic fluids under your hood today!
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