Which average priced synthetic oil would you run to tackle varnish?

[Hohn]

This is a great data point. Thank you. Can you remind us what your oil change history was prior to VRP? OCI and oil used? I know you mentioned it elsewhere. I just cannot find it.

Changed on the OLM with what I thought was good oil. Various synthetics over the years but mostly PP for the last 100k miles or so. Never used oil but got very varnished.

 

[OVERKILL]

What range of oxidation do AN or PAO or GRP III show in a VOA?

None, around zero.

 

[ChrisD46]

In well serviced engines that used M1 oils at reasonable intervals engine internals look like metal is supposed to look (clean) . SOPUS oils used similarly would usually leave engine internals with a yellow cast but clean otherwise . I don’t know about Castrol. Since M1 performed so well , I stayed with it until a recent VRP experimental run for potential ring carbon deposit cleaning (a different animal than varnish) and to see if I can improve moderate oil consumption.

 

[factorytuned2012]

Mobil 1 HM or Pennzoil UP

 

[edhackett]

Zero or near zero for PAO and AN, due to lack of oxygen atoms. I expect non-GTL Group III to have a very small concentration of oxygen containing molecules because the processing tends to get rid of the oxygen-containing molecules present in crude oil. I expect GTL to be similar to PAO in terms of lack of oxygen content. Whether dissolved oxygen gas in oils registers as oxidation in the test devices is an interesting question.

Oxygen gas will not show up in FTIR analysis. FTIR is looking at the electrical polarity of bonds between two molecules. Diatomic molecules of the same element such as O2 and N2 are symmetrical and have no polarity to their bonds. They don't produce an infrared signal that is detectable by common infrared based laboratory analytical techniques.

Ed