CJ-4 Oil questions

[mbacfp]

Have a question about the additives in CJ-4 motor oils that separate the soot, dissolve varnish (engine waste), etc. from the motor.

Does the oil filter catch most of it? The contaminants that aren't caught by the filter...do they stay in suspension for long periods of time in the oil?

Thanks!

 

[Chris142]

Stay in suspension.

 

[Pontual]

Detergents (common uses are calcium sulfonate, others use sodium sulfonate) detach the dirt from engine parts. But what keep dirt in suspension is mostly Polyisobutilene and anhydrid succinimides. A few synthetic HDEO uses group V in the base composition, that helps on solvency, acting like detergent and dispersant, too.

 

[dnewton3]

Yes - soot and insolubles are generally sub-micronic in nature, at least when they start out. Even when they get "big", they are still very small relative to a typical FF filter element. So they stay in suspension (as long as the add-pack is not overwhelmed) and are not filtered out. A BP filter will catch many more of these, but still they are not overly effective at anything 2um or smaller. So a lot stays in suspension until you OCI.

BTW - it's not just CJ-4 that does this; most any decent motor oil today has the ability to do this, but to varying degrees of duration based upon intended market application.

 

[mbacfp]

Thanks to all. I appreciate the knowledge.

 

[Joel_MD]

Soot particles are so small that most are not trapped by an oil filter. In my experience there is nothing harmful about normal amounts of soot in engine oil. On the last UOA (link) on my Cummins the insolubles percentage was calculated at 0.2 after 14k miles.