How can an oil be rated at "0W"?

[tdi-rick]

If they just listed the outright kinematic viscosity at say, -25*C, 0*C, and 100*C on the label rather than having to find a TDS and run the numbers through the VI calculator it would be a lot more meaningful.

or am I just a nerd ??

 

[Drew2000]

Originally Posted By: wannafbody
Some oils are rated for -20 to -59 degrees farenheit. Not sure their is much need for paasenger car oils that operate at colder temps. I could see some demand for heavy equipment that operates in Canada, Alaska and the artic circle though.


I would bet that at those temps, heavy equipment and trucks are either plugged in, or just left idleing indefinitly anyway,

 

[tom slick]

Originally Posted By: TwsT
Please educate me.

How come, for example, Amsoil ATM 10W30, a 10W oil can have a pour point of -50deg.C.
But Amsoil XLM 5W20, a 5W oil gives a -43deg.C pour point?
So which one performs better in very cold weather? Thanks.


Think about this; anti-freeze/water is more viscous than plain water yet anti-freeze flows at much lower temperatures but during normal operation perform the same function. Engine oil is a mix of chemicals, some of which specifically modifies the pour point. The pour point is not taken into account in the SAE system.

 

[XS650]

Originally Posted By: tdi-rick
If they just listed the outright kinematic viscosity at say, -25*C, 0*C, and 100*C on the label rather than having to find a TDS and run the numbers through the VI calculator it would be a lot more meaningful.

or am I just a nerd ??

Back to the future.

The problem with using plain old kinematic viscosity at the cold end of the scale is that it doesn't tell you how the oil will act when being pumped or sheared during the starting process.

Around 40 years ago, the xW number was based on an ordinary viscosity test at 0F (-18C). They went to the present 2 test method at temps closer to the minimum temp the oil is good for because the old 0F test method didn't tell you how the oil behaved at the practical minimum temperature limits.

 

[Drivebelt]

I never thought of that, 0W = zero weight = weightless. Anti-gravity oil. I guess that would mean GC flows uphill.