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Many people believe that the low Winter weight oil ratings like a 0W or 5W means that the oils are too thin to pump or lubricate properly.
The API/SAE designation for multi-grade oils includes two grade numbers; for example, 10W-30 designates a common multi-grade oil. The first number associated with the W is not rated at any single temperature. The "10W" means that this oil can be pumped by your engine as cold as a single-grade 10 weight oil can be pumped. So a 5W can be pumped at a lower temperature than 10W and 0W can be pumped at a lower temperature than 5W.
The second number, 30 in our example, means that the viscosity of this multi-grade oil at 100°C (212°F), the typical engine operating temperature, corresponds to the viscosity of a single-grade 30 oil at same temperature.
For example -
0W viscosity is rated 6200 cSt at -35C.
5W viscosity is rated 6600 cSt at -30C.
10W viscosity is rated 7000 cSt at -25C.
15W viscosity is rated 7000 cSt at -20C.
20W viscosity is rated 9500 cSt at -15C.
However, for example Mobil 1 0W-30, 5W-30, and 10W30 oil all measure between 62.0-64.8 cSt at 40C, and 10.0-11.3 cSt at 100C. The Winter rating only measures the lowest pumping temperature of the oil, not the viscosity at more modest temperatures.
So when multi-grade oils designated 0W, a 5W, or 10W are measured at some slightly elevated temperature like 32F (0C) they will all have nearly the same viscosity. That is the purpose of a good multi-grade oil, to offer the appropriate viscosity over a wide range of temperatures.
REM in Seattle
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1984 Saab 900T; Cherry Red; 3-door; 5-speed; 242,000 miles (RIP)
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