Shearing oil ?
- Thread starter Fbear
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5w30 with their high VI are shear prone. They are supposed to remain in grade but as we've seen on many UOA some dont. Most Oil Cos are formulating on the thin side of SAE 30 - Chevron has been sucessfull with the Havoline DS. Ive noted shearing in my toyota which is HIGHLY sensitive to oil viscosity with Mobil 5K and PYB - but I was still in break in which is tough on oil. Fuel dilution is a more common issue. I wonder if top oiling at 0.5- 1% would show reduced fuel dilution? - It should.
To answer your question simply, the more mechanical action on the oil the more it will shear, So pumping and spilling at 5K rpm v. 2k rpm would have a more pronounced shear effect. That is, Unless you have adaptive weartronic molecules which are somewhat "sturdier" than the EPDM based junk from 15 years ago
Fbear - The general perspective is that for any given oil [like 5-30], the full synthetic version will shear less than the dino .
Same for gear lubes.
It seems to take 2-3k or more in normal use to get noticeable shearing of engine oil, if any.
This situation exists, but is rarely a real problem.
Same for gear lubes.
It seems to take 2-3k or more in normal use to get noticeable shearing of engine oil, if any.
This situation exists, but is rarely a real problem.
Gear tooth contact is one area where the viscosity index improvers shear most readily. The gear drive between dual overhead camshafts, even when the engine has timing belt drive of one of the camshafts, is one prime area.
Yes, oils shear less because the higher Group oils have an inherently higher viscosity index so they need a lower content of viscosity index improvers, also called viscosity modifiers. Plus, viscosity index improvers are better and shear less. And, as always, lower cost (lower quality) VIIs don't hold up as well as higher cost & quality VIIs.
Here's the blurb from one major supplier of oil additives, Lubrizol: http://www.lubrizol.com/ViscosityModifiers/Asteric/default.html Look at charts #1 & #3 on their cuties graphic.
Yes, oils shear less because the higher Group oils have an inherently higher viscosity index so they need a lower content of viscosity index improvers, also called viscosity modifiers. Plus, viscosity index improvers are better and shear less. And, as always, lower cost (lower quality) VIIs don't hold up as well as higher cost & quality VIIs.
Here's the blurb from one major supplier of oil additives, Lubrizol: http://www.lubrizol.com/ViscosityModifiers/Asteric/default.html Look at charts #1 & #3 on their cuties graphic.
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