其它相關資料
http://forum.jorsindo.com/forum. ... 9&page=6#pid7666260
The clearances between the crankshaft journals and main bearings are tighter, for one.
In Josh's case(指0W20), his 15W50 racing oil may be too thick to flow quickly enough to fill the spaces between the crank journals and main bearings while the engine is running.
https://forum.jorsindo.com/forum ... 7&page=1#pid7840619
四輪車に採用されることが増えた0W-20等の低粘度オイルを、8,000rpmを超える高回転域を多用することが多いオートバイ用エンジンに使用すると、油膜切れによるバビットメタルやピストンリング、カムシャフトジャーナルなどの摩耗や焼き付きが発生しやすい。
https://forum.jorsindo.com/forum ... 0&page=6#pid5696762
HT/HS is a measure of dynamic viscosity, it represents the oil’s thickness within the vital hydrodynamic bearings of an engine. It is the most important measure of how well the oil will perform as a hydrodynamic lubricant. HT/HS is measured at 150°C which is a worst-case temperature for most engines. The higher the HT/HS, the stronger the hydrodynamic film in the engine’s bearings. Thus, the correct HT/HS is more important than the KV100(SAE Grade) when selecting oil.
Some constituents of oil, particularly Viscosity Index Improvers(VIIs), change their chemical makeup when subjected to repeated cycles of physical shearing. The physical stress of shearing “clips” the longer molecules into shorter ones, thus permanently reducing the oil's viscosity. In many oils designed to improve fuel economy this effect can be quite pronounced, often reducing the oil's viscosity by 10% or more and resulting in a reduction in viscosity grade from 30 to 20. An oil's resistance to permanent shear is known as its shear stability. Motor oil certification specifications set minimum levels of shear stability with the European ACEA specs being more stringent than the American API/ILSAC specs.
Ideally the lab would measure HT/HS, and many offer that as an add-on service costing hundreds of dollars, but that's obviously cost prohibitive, so we use KV100 as a proxy. Luckily, automotive engineers have studied the relationship between KV100 and HT/HS, and it's relatively predictable. HT/HS is generally reduced by half the amount that KV100 is reduced due to shearing.
In practice most Group III synthetic oils shear 10-15% in use, Ester/PAO oils somewhat less, conventional oils somewhat more. If your oil shears more than this or if your usage results in thinner oil through fuel dilution, a thicker oil or one more resistant to fuel dilution is a wise choice. Oil's flashpoint is reduced primarily by the presence of fuel, but can also be reduced through shearing and other mechanisms.
The presence of fuel in oil will lower the flashpoint and viscosity through damage to base stocks and additives, substantially shortening the oil's service life. Properly sampling the oil after heating it thoroughly should remove short term cold-start fuel from the oil but many engines regularly run rich and substantial fuel dilution over the long term can be the result.
https://forum.jorsindo.com/forum ... e=1&authorid=363198
https://forums.nasioc.com/forums/showthread.php?t=2714154
エンジンオイル 劣化
http://kurumanu.com/engineoilnituite/engineoil.rekkasuruto.html
https://www.honda.co.jp/study-mo ... sai-page/index.html
本文最後由 phos 於 2019-8-4 19:50 編輯
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