mountainmotor
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But how do you know it is PAO base oil for sure?
Mobil refuses to say what it is. If I look at shear results, it makes me wonder, but it could be a cheaper ester package causing more shear than I would like to see.
The MSDS of course. Also easy to see it in the Total Acid Number <TAN> numbers of new oil sampling. < fourier transform infrared spectroscopy> aka FTIR . Esters are acids and the TAN is relative high when tested.
An ester base oil does not have anything to do with shearing or thinning of the oil formulation. Esters are used to balance seal swell when used in polyalphaolefins which lack that ability and helps the solubility of large additive packs and more since they are polar . Some additives used in mineral based oils just are not needed when an ester is around. Pour Point Depressants and other.
That said, the shear or reduction in starting viscosity you are talking about comes from permanent shear of the Viscosity Index Improvers used and most often in motorcycle engines, more fuel is present that the lab results actually show. Fuel in the oil can easily reduce the viscosity and be the culprit even when the lab results still show a high flash point.
BTW , when you see an oil label that says it's ester based , that does not mean the large component of base oil is ester. I see it's becoming somewhat a trend with some foreign made oils.


