Motor oil rookie
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- Joined
- May 3, 2025
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- 206
Thank you. That oil became thick instead, 8.5 to 9.5. Now this is another problem, oxidation winning and there is no shearing to stop it. This is not cool. I got excited that No VII oils remain at virgin viscosity all the time but apparently it is not the case. What oil is this?Keep in mind, there are a variety of different VII polymers used and they vary in their shear resistance from "shear easily" to basically not at all.
Base oils also oxidize at different rates; have different levels of oxidation resistance and antioxidants are used to reduce the propensity to oxidize.
Formulators do indeed try and balance visc loss through shear with oxidation, and, as @userfriendly noted, light ends flashing off, which varies depending on the base oils used. However, a bigger factor in recent years, since the introduction of DI, has been fuel dilution.
This is what happens when you use shear stable VII's with PAO as the dominant base in an application that doesn't fuel dilute (sample 2 is VOA):
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