Quote:
Originally Posted by m6pwr
1700 ppm in TWS has got to be an error of some kind, maybe contamination of some sort in the lab or in the sample handling. Mobil racing oils have 1700 ppm zddp and Mobil (on their web site) recommends it only for racing (and probably very short drains) and not for street use. I have a voa of TWS done in Jan 2009. It had 641/796 zddp, but was rated API SJ. That low a level of zddp would today qualify it as a low saps API SN fuel economy oil (good for your Tahoe). It must have had some ester in it, like castor oil, for antiwear, which wouldn't show up in a voa.
Back to Mobil 0w40: the buzz on BITOG is that it has recently been reformulated, as well, and is now a better oil - - it used to shear back rather quickly.
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I think that is the kicker with the ester, our machine is one that the oil manufacturer themself uses. It is about a quarter of a million dollars and is like no other really. It has a built in alogarithm to factor in the ester base material. I have wondered about the error but have done a calibration then tested again then tested a basic quaker state synthetic 4x4 oil right behind it and it showed up as 850 on zinc so I am not convinced if it is a machine error or not. I checked a later bottle of the new Edge 10-60 and it shows up as 950ppm.
The 0-40 has been reformulated a while back, when it went to the sn rating it changed and for the better. This is why I run it in the M and I know a few other folks do as well. I change it every 3k miles so if it does shear it is not an issue anyway.