Originally Posted By: CATERHAM
Originally Posted By: Skid
Originally Posted By: Shannow
Originally Posted By: CATERHAM
Better fuel economy may be the least important advantage of thinner oils. The main advantages are less engine wear particularly on start-up and
OK, CATERHAM ...again...please show, in industry standard testing, SAE papers, ASTM papers, or any other credible source, which isn't fluff from manufacturers, where thinner oils provide less start-up wear than any other grade rated for the temperature.
Can start with Sequence IV if you like, which is the industry standard for warm up wear.
I don't think thick/thin matters wrt startup wear unless you're at such an extreme that you can't pump the thick stuff at all or it won't drain back to the pain.
Some points (I'm talking plain bearings here, not cams, rings, etc):
1. You start out in boundary lubrication whether thick or thin.
2. You transition to hydrodynamic lubrication when the engine starts rotating.
3. A thicker oil should form a film faster (thicker film at a lower rpm), but the engine might spin faster with a thinner oil, so I think it's a wash.
4. Don't bother talking about thinner oil getting to the parts faster because there is residual oil between the journals and the bearings to form the films. It's not like your engine disassembles itself every time it shuts down and cleans off all the oil. Your bearings are never dry, and the residual oil will not burn off that fast.
Anyway, I think thick or thin for startup wear is a wash.
I think every auto manufacturer would disagree with you and remember the motivation for the development of the as light as possible on start-up OEM 0W-20s was to reduce start-up wear with the constant on/off cycles of hybrid engines. And when these engines are started, there is no gradual warm-up but instant elevated rpms under load.
Back to the discussion of motor mud I mean the 20W-50 grade, even engines with a fairly high oil pump relief (by-pass) setting will be in by-pass mode instantly on start-up even at room temperature on idle. So yes you will have reduced oil flow on start-up and much of the time during warm-up. And that is the recipe for increased engine wear particularly if you're indifferent to keeping the rev's very low or are otherwise indifferent to any sort of warm-up regimen.
Of course this applies to all heavier grades but to a lesser extent. All the more reason to run the lightest oil specified with the lowest possible KV40 spec'.
What's the science to back up your opinion? Your posts sound like religion/politics to me. An opinion with nothing to back it up.
Hybrid engines are proof that startup wear is not that big a deal. And yes, these hybrids avoid gradual warm up, which is better for wear because you want to minimize the condensation. There's even some exhaust heat recovery in some of these hybrids to heat up coolant faster.
If you want to talk auto engineers and engine wear, then let's refer to Lubrizol's tool and look at the various manufacturer's specifications for oil:
http://www.lubrizol.com/EngineOilAdditives/ACEA/RelativePerformanceTool/default.html
Where's the "startup wear" parameter there? There is none. There's just one category for wear, and it's "wear." And all the standards that have a somewhat high rating for wear (BMW LL-01, MB 229.3, etc.) require an HTHS of at least 3.5, which is a medium viscosity, not a thin viscosity. I think the auto engineers have spoken.
