High VI and durability in a front fork oil?

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As per title

Theres a custom oil tuning shop near where i live that says they are capable of tuning VI indexes of 100-500
for hydraulic oils

It says they are using mainly Group 4 PAO's

As I dont acces to Silckolene RSF 15(VI= 235) and can calculate the viscosity that I want , i would like to know about High VI index and the factor it plays in the overall durability / shearing of the oil.

Said fork oil is going to be used in hi temperature conditions (35-60 deg C)

Would love to hear your views
 
What is an oil tuning shop? They are adding a top treat to the oil to improve the VI?

Any VI above 200 is exceptionally high for hydraulic fluid - and I only know a couple of polymers that will reach this VI without shearing out of grade when in service. The skeptic in me says your "tuning shop" does not know what they are talking about.

Because of the temps, I would probably suggest going a grade above what the OE recommends for 20C (e.g. ISO 68 instead of ISO 46). Using a high VI fluid would be beneficial IF the fluid is also shear stable. If you go to DYNAVIS they have a very good explanation of shear and viscosity in hydraulic pumps and how it effects efficiency.
 
They may just be dumping a VI improver in, which can shear apart and negate any gains it makes.

I think more info is required on this shop and what they claim to do.
 
VI for shock oils can run to 600 VI or so what do you need to know? IMHO PAO's will NOT go to 600-625 VI it takes a special base stock and VII.
 
Thanks for the answers, finally got the RSF 10 and 15 WT on special order !!

BTW will the RSF fluid absorb water faster than a comparatively low VI mineral based fork fluid ? The area i live in is damp as [censored] and rains often for days at end; bike is parked outdoors fyi.

(the one in the rsf is an unspecified ester )
 
Originally Posted By: PhillipM
If your seals are good it shouldn't be a worry...



This. Just minimize how long it's exposed to the air in an open container. Typically, oils that absorb water will turn back into the 2 components used to make them - one of which is a nasty acid. You can also heat the oil to 220F to evaporate any water content out of it - but you risk shortening the life of it a good bit.
 
I stock a synthetic with a 313 VI that is great for forks. Doesn't thicken up in cold weather, and more importantly does not thin down in the high temperatures produced by the high compression in the forks.

In the US you can probably find Pentosin CHF 11S or CHF 202
 
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