I have a problem about hydracloric acid building in the engine oil after the vehicle sits without the engine running for several days. I have noticed that this effect is only happening to the older engines with a EGR add on. Do you have any information related to this.

Hi Roy,

EGR will definitely increase your soot loading on the engine oil but I have not heard about hydrochloric acid building up in an engine. Chlorine is not part of any lubrication make-up (not engines anyway) and the only way it could get in there is by external contamination.

A couple of questions:

Are you referring to acidity or specifically hydrochloric acid?

Is there a possible source of chlorine in the vicinity? (i. e. is the unit working in a chemical plant)

The EGR units are add-on, how about contacting the supplier and asking if these units are acid cleaned before dispatch to customers, there might be a residual chlorine deposit as a result of improper flushing techniques ...

Are these engines running hotter than usual, as this might accelerate oxidation and acid formation.

How does the rest of your used oil analysis on these units look?

Have a terrific day.

Are you using an oil additive package, like Power-Up? This may be the source of clorine.
JimF