STP oil add response regarding diesels

[JHZR2]

Sent a message to STP asking about using their adds, especially the 4-cyl additive to augment zddp in old diesel engines. I got the following response:
Quote:


Thank you for contacting us about STP Oil Treatment. We always appreciate hearing from our consumers.

Unfortunately, we do not have a product we can recommend for a diesel motor. Our oil treatments do contain ZDDP and are great for classic cars with flat tappet cam motors, however, not diesel motors. None of our oil treatments will change the viscosity of the oil when used with 4 to 6 quarts of oil. The amount of ZDDP in our product is proprietary.
Again, thank you for contacting us.




Wonder why not-suitable for diesels. Perhaps add clash with detergents?

Also funny zddp not at least given per the msds, which says 1-5%, and also gives viscosity of product.

I guess I'll go with my advanced molabrew, lc20, schaeffer's 132 and redline break in zddp additive for use in my diesels.

 

[DieselTech]

I don't believe it's just in reguards to ZDDP. Foaming is a huge issue with diesel. If their product is not formulated for it, it will do more harm then good. IMPO ALL oil additives need to remain out of a diesel engine. There is no benefit to using them in a HDEO

 

[m37charlie]

Originally Posted By: JHZR2
I guess I'll go with my advanced molabrew, lc20, schaeffer's 132 and redline break in zddp additive for use in my diesels.


I contacted Redline and tried to find out the carbon number and structure of the alkyl groups in their breakin additive. Trying to figure out if it was heat-stable (long chain or secondary/tertiary) or heat-labile (short chain). If the latter, not appropriate for diesel use.
They wouldn't give me the answer.
I suspect it is more "active" ZDDPs since it is labelled as "breakin additive". If so, it is likely to break down quickly in the upper ring belt and just cause a layer of lacquer/varnish.
So I'm not going to use it.
Even though my engine has flat tappets, cam operated injector pumps (rollers) and my oil has "only" 1200ppm Zn.

Charlie

 

[JHZR2]

Interestingly I emailed Dave too... Got this:

Quote:

Thank you for contacting Red Line Oil, the Break In Additive doesn’t reduce lubricity, but used with a petroleum oil allows the rings to seat in a fresh engine where our synthetic oil could impede that process. It can be used to fortify a CJ-4 oil though I would expect most would still contain just under 1200 ppm phosphorus, still good anti-wear protection for flat tappet cams.