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Originally Posted by go_a_way1
I wouldn’t change my viscosity for a DD because 90% of engine wear doeshappen at cold starts and the 0W-20 will provide better protection on thosecold starts. Yes I know I could go with a 0W-30 but I have been told by anumber of people in the industry that oils that have a wider viscosity rangetend to provide less protection in areas like the camshafts or other high pressuresituations. I used to run Castrol titanium,but have now switched to their professional OE that still uses the sametitanium additive technology.
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If you don't have enough protection at severe conditions, and your engine has metal to metal contact because of not enough additives or oil viscosity, then the cold start wear is meaningless. You really want to avoid boundary lubrication events:
http://www.bobistheoilguy.com/states-of-lubrication/
I don't believe that 90% wear is accurate anyway, probably just marketing. I can look around for some SAE papers on that though because I see it thrown around a lot. Whether or not your wide viscosity spread oil can provide protection in various parts of the engine depends mainly on the quality of base stocks, the oil additives, and the quality of viscosity modifiers used. Your statement was probably correct 10-15+ years ago, but there have been huge improvements in oils and oil additives over the past several years.
Here's some excellent information about viscosity modifiers by someone that is in the lubrication industry:
http://www.bobistheoilguy.com/forums...pics/3788899/1
I'll also add that there are some very excellent 0Wx racing oils:
Mobil 1 Racing 0W30, 0W50 (track only, not street/track)
Red Line 0W20, 0W30, 0W40,
Motul 0W20, 0W40
and many others.
If I was looking for the optimum oil for hard driving, I would focus on High Temp High Shear and NOACK Volatility (evaporation at 300C). It's harder to find NOACK, but HTHS is a little easier to find. All Euro's oils that meet ACEA A3 have a high HTHS (30 grades and above) and so do race oils. This is why I would run a Euro 0W30 over a Resource Conserving/GF5 5W30. The GF5 5W30 will shear to a 20 grade in many conditions due to the low HTHS as these oils are designed for fuel economy.
Also note this high HTHS 0W30 available in Japan:
http://www.pleiades-zero.com/?page_id=2
