Oil discussion (pressure, grades, viscosity, etc) - repost from Ferrari Chat
 

I found this thread many years ago, and figure it's helpful for those wanting to learn more about engine oils.

Feel free to read/bookmark, the info has served me well over the years.

http://ferrarichat.com/forum/faq.php?faq=haas_articles

Long story short, oil pressure is the important factor in your engine oil's performance. Everyone freaks out about how thin 0W-20 is, but it's not a big deal at the ideal temps.

-alex

Oil pressure isn't the important factor as the article says. Oil pressure keeps the oil flowing through the bearings. Oil flow is the key. Oil flow keeps oil temperature in the bearing at an acceptable level. Bearing separation is achieved by the wedging action of the oil film under rotational forces which is one reason lugging an engine at very low rpm can damage the bearings, not because the oil pressure is too low but because the rotational speed of the bearing is too low. Film strength affects this quality of the oil, higher film strength generally gives better protection.

People tend to think the higher viscosity protects because it resists the forces moving the bearing and journal surfaces together. This is incorrect. Higher viscosity may be needed to keep the oil flow rate correct for your engine design. If the engine is designed for low viscosity oil then using higher viscosity can damage your engine.

If you put higher than recommended viscosity oil into your BRZ engine you can slow the flow rate down to the point the oil within the bearings gets too hot. Oil pressure will be high but flow rate will be low.

Same thing in a much better-formated text is here.

Good thread about oil film in bearings here. Lots of "noise" there, but a couple of good posters in that thread (Shannow and Molakule).

I always like to point out that Dr. Haas on Ferrarichat and bitog is a plastic surgeon. ;)

-Dennis