Originally Posted By: Merkava_4
Originally Posted By: Jim Allen
1) You are misrepresenting a situation to suit your assertion that thicker is always better. Plus, you have seen only a tiny, miniscule fraction of the UOA Blackstone has produced, so using the term "ever" is wild speculation at best.
I'll respond to that first statement because it appears to be directed towards me personally:
I do not believe that thicker is always better. When I see high wear metals and the oil being tested is 5W-20 or 5W-30, and the silicon ingestion is low, my immediate assumption is that the viscosity is wrong for that engine. What do I base that assumption on? I base that assumption on the single most important factor impacting on how an oil interacts with an engine; its viscosity. If I'm wrong in making that assumption, then you need to tell me. We're all here to learn the correct way; you may as well start with me.
Well, Garak said most of what I would have said, RE interpreting the contaminants in the snapshot UOAs seen here as any indicator that a thicker oil is needed. To prove that it does, you'd need dozens of samples taken on the thinner oil and then dozens more on the thicker oil, the UOAs from each oil taken in with the engines undergoing roughly the same conditions, and with identical additive packages, to prove that the heavier oil produces lower metals, due to the viscosity difference alone. It's proven that in some conditions, usually harsh and hot operating conditions, an engine can benefit from a thicker oil but usually that is covered in the OEM manual specific to that engine.
I'm glad to hear you say you don't think thicker oil is always better. Many of your previous posts and responses left me with that impression and I'm glad to hear I was wrong.
But, no, I don't think viscosity is the single most important factor. Try whichever viscosity oil you like without additives and see how long the engine lasts. Additives will make or break any oil and you could call them an equalizer at any grade. And without the correct viscosity, the best additive package in the world is no good. It's all about synergy, all the parts working towards a better whole. I think it's a mistake to focus on only one aspect of the whole. That said, if you look at some of the work Lubrizol is doing on low viscosity gear oils < www.axlefacts.com>, you can see that additives are beginning to go past that 50/50 mark in terms of importance.