Originally Posted By: BuickGN
Can one of you enlighten me as to what these nooks and crannies inside an engine are? I see post after post referring to these things and I guess I'm not educated enough to know what they are. They must be very small, because only a 0w-20 can even reach them even though many bearing clearances are .002 or less. In fact I've never seen them in a teardown. Where should I start looking?
I can also claim that after working on engines for most of my life, I have yet to find those nooks and crannies. I need someone more educated and experienced than I to give me a lesson or two
But seriously, I know that many people have been using thin oils with no problems to date. That is fine, but that is also not the argument here. The problem that I believe BuickGN is trying to pick at here is that some people have the belief that their engine can ONLY take thin oils. This is fundamentally wrong, and being an engineer, I simply don't understand that. A 0W20 is extremely thick at -40C. If an engine could only work correctly with a 9 cSt oil, then until that oil gets to 100C, the engine simply wouldn't work if that were true.
Also, the weights of oils at 100C are within a small spread (8-15 cSt) for 20, 30, and 40 weights. However, the weights of cold oils to hot oils are contained within a MUCH larger spread (55-120 cSt). At operating temps, you will not convince me (or any knowledgeable and experienced individual) that a hydraulically actuated solenoid will work with a 9 cSt fluid, but not with an 11 cSt fluid. The difference is so small, that you would be hard pressed to measure it let alone feel it in your engine.
Flowrates... JAG posted an article comparing 20, 30, and 40 weights for power and various other things. The article was not specifically discussing flowrates perse, but did measure them at an RPM near redline. This means that the oil pump would have been in full bypass, and theoretically, a thinner oil would yield more flow due to the bypass condition. And yes, there was a difference... It was in the range of decimal places! So yes, there is a small difference in flowrate - not much though. And of course, there is virtually NO difference in flowrate when the pump relief valve is not in bypass (such as low rpm cruising).
We have seen time and time again that engines recommending 20 weights here, take 30 and 40 weights elsewhere. YES - the 20 weights work fine! No argument there! But the 30's and 40's also work well - and one cannot argue that either, or we'd see engine failures of all kinds in Europe, the middle east, and Australia - which we don't.
