What the W means on the oil!!!

[70' GMC]

I read on a calender which is auto related, and it said that the "W" meant winter NOT weight. So if it says 10W or 20W it means 10 degrees in winter or 20 degrees in winter. I hope someone has some more info on this.

[BarryB]

The lower the numer the easier it flows in the winter so a 5W would flow well in winter climate's. Thats my understanding of it. Now the latter part of oil identification 30 40 50. I have now idea.

[wibilly]

i think the whole multi viscosity oil thery is a farse where i come from it all flows like 85-90 in the winter

[WorkinLonghorn]

This is from Wikipedia;

The API/SAE designation for multi-grade oils includes two grade numbers; for example, 10W-30 designates a common multi-grade oil. Historically, the first number associated with the W (again 'W' is for Winter, not Weight) is not rated at any single temperature. The "10W" means that this oil can be pumped by your engine as well as a single-grade SAE 10 oil can be pumped. "5W" can be pumped at a lower temperature than "10W". "0W" can be pumped at a lower temperature than "5W", and thins less at temperatures above 99°C (210°F). The second number, 30, means that the viscosity of this multi-grade oil at 100°C (212°F) operating temperature corresponds to the viscosity of a single-grade 30 oil at same temperature. The governing SAE standard is called SAE J300. This "classic" method of defining the "W" rating has since been replaced with a more technical test where a "cold crank simulator" is used at increasingly lowered temps. A 0W oil is tested at -30°F, a 5W at -25°F and a 10W is tested at -20°F. The real-world ability of an oil to crank in the cold is diminished soon after put into service. The motor oil grade and viscosity to be used in a given vehicle is specified by the manufacturer of the vehicle (although some modern European cars now make no viscosity requirement), but can vary from country to country when climatic or mpg constraints come into play.

[corn]

Polymers are added to a light base oil(5W, 10W, 20W), which prevent the oil from thinning as much as it warms up. At cold temperatures the polymers are coiled up and allow the oil to flow as their low numbers indicate. As the oil warms up the polymers begin to unwind into long chains that prevent the oil from thinning as much as it normally would. The result is that at 100 degrees C the oil has thinned only as much as the higher viscosity number indicates. Another way of looking at multi-vis oils is to think of a 20W-50 as a 20 weight oil that will not thin more than a 50 weight would when hot.

Forgot, W stands for winter...

[70' GMC]

So if I change the oil in the winter, would I have to get 5W-30?

[panhandler62]

In North Carolina? Shouldn't really be an issue.