Originally Posted by racin4ds
Right now, I'm running Rotella T6 in my Passat, and all I hear is people on the VW forums cringing and yelling at me because it is not a Low SAPS oil... I mean, my car might burn an ounce or two of oil on an OCI... is that really enough to hurt something??? I highly doubt it....
Do
not run an HDEO in a high-performance gasoline engine, like one with a turbocharger.
HDEO's and PCMO's are designed differently
with different goals.
The problem with an HDEO in your application is that it more than likely uses a hydrogenated-styrene star VII instead of an olefin copolymer (OCP) VII used in PCMO applications.
These star VII's are
high-(permanent)-shear-stable but
low-thermally stable, i.e.
dirty, VII's. They retain their viscosity boost well in the long run, but they form more engine and turbocharger deposits, as they run dirty. They are more popular in HDEO application, where viscosity and permanent-shear stability is more important than engine deposits. A car engine doesn't care about shear stability nearly as much.
On the other hand, olefin copolymer (OCP) linear VII's are
mid-(permanent)-shear-stable but
high-thermally stable, i.e.
clean VII's. They experience moderate permanent shear, but they run much cleaner. They are very popular in high-performance PCMO applications as well as most other PCMO applications as a result.
I discussed a nice article about the deposits caused by star and OCP VIIs:
GM turbocharger test: No correlation for deposits with TEOST 33C or moly
Therefore, in the long run, running an HDEO may cause problems in your turbocharger etc.
Of course, this is only one of the possible problems.
There is no reason to stray away from a PCMO specifically designed and certified for engines like yours and run an HDEO designed with quite different priorities in mind, as in the proper VII selection I explained above.
You're right though SAPS is not nearly as critical, although higher SAPS will decrease your spark-plug life among other things, such as increasing ash deposits on your piston crowns, and a mid-SAPS oil (SA ⤠0.8%) may be beneficial over a full-SAPS oil (SA ⥠1.0%).