ZDDP vs. Detergents in engine oils.

[Scott_Tucker]

I just read an article written by Lake Speed Jr. of Joe Gibbs racing in the October-December issue of "Engine Professional" - the Automotive Engine Rebuilders Association magazine. It talks about the fact that both ZDDP and detergents are polar molecules and have an affinity for metal. It states that modern engine oils have decreased levels of ZDDP (which we are all well aware of) and increased levels of detergents. It seems to be saying that increased levels of detergents can displace the benefits of adding additional ZDDP (through a pour-in additive) because they are both competing for the same real estate on the metal parts.

My question is: Is there anything on an oil analysis that can reliably tell you the balance between ZDDP and detergents in the oil? Do detergent levels even show up on an oil analysis?

 

[JHZR2]

I agree with the fighting for surface. That said, there is an overabundance of both types of adds in the oil. Because of this, the add with the higher adsorption energy should displace anthing else. It is competitive adsorption, so not sure I accept all claims.

Concentration of each additive should be seen in relative ratios in a VOA or UOA. Certain metals are the analogs for additives.

I suppose the key is what adds serve as EP/AW as well as detergent/dispersant?

 

[Scott_Tucker]

So what do the detergents normally show up as on the oil analysis and what would be a good range? Also, just out of personal interest, what chemicals are the detergents normally made from? Are there different types of detergents being used among the manufacturers?

 

[m37charlie]

The detergents are Ca/Mg/Na sulfonate/phenate/salicylate. The antiwear additive is mainly ZDDP coumpounds, showing up as Zn and P. The dispersants are nonmetallic organics.

Charlie

 

[Steve S]

The additives can overlap in their duties and they are blended and balanced , look at the used oil analysis and voas to see the similarities between the brands and additives used.