Quote:
Originally Posted by RPM90
Yes, it's been a more common useage in the the M engines, but they also rev a lot higher.
Still, using the temps you quoted, it makes sense that the "go for it" oil temp is around the same temp as the thermostat would open.
In the M cars, have you noticed at what temp the coolant gauge is at when the oil temp gauge is showing 167F?
a 0w40 oil is thicker than 40 weight below 100C and flows less easily, with a higher likelihood that the oil pump won't be able to pump a high enough volume of cold oil to keep the engine well lubricated at high revs.
That's not right. "Viscosity" is the resistance to flow. So a 30 weight oil will be less viscous than a 40 weight when hot. Higher weight oil is, or should be, MORE viscous and thins less when temps get really hot.
A 0W40 is a "Winter" rated oil, meaning in sub freezing temps the oil retains it's ability to flow, or low viscosity. The "40" rating means that at higher temps it's just like a straight 40 weight oil, greater viscosity.
Amazing stuff this. Of course, go too hot and the oil starts to lose it's viscosity.
At cold temps, straight 40 weight would be too viscous to flow properly, and the pump would have a heck of a time getting straight 40 to flow in sub freezing temps, and the oil will be too thick to properly lubricate rings, bearings, etc...
Here's a good read on viscosity, and not the part/s of the PDF where there is a relationship between thermostat, proper engine operating temp, and oil temp.
http://www.zddplus.com/TechBrief13%2...0Viscosity.pdf |
The current ///M cars do not have a water temperature gauge, just an oil temperature one. A warning light will illuminate if the engine is over temp.
I wasn't talking about a straight 40 weight oil in my comment, maybe I should have phrased it better - the 40 part of 0w40 (the 40 weight, not straight 40) is measured from a specification perspective at 100C. At any temperature less than 100C, the oil is going to be thicker than the engineers envisioned by specifying that weight of oil, it is going to act like a heavier weight oil (just because it is cold) and flow through the engine in a more viscous manner, meaning that the oil pump will have less flow than if the oil was at the specified temperature for the grade measurement (100C)