Molybdenum vs. ZDDP

[RZT5]

I'm trying to decide if I want to run Redline in my M156. I did a VOA on the genuine Mercedes-Benz 229.5 oil that the MB dealer network uses in these engines to compare to Redline. The RL of course has more additives across the board, but the big difference is lots of moly in the RL sample; there is none in the MB oil.

Question 1: Does moly compete with and displace zinc/phosphorus (ZDDP) when bonding to metal surfaces?

Question 2: It is primarily the high lift cams and flat valve tappets I'm concerned with; does ZDDP or moly provide a more protective layer?

Thanks for your input!

 

[deven]

Molybdenum is more of a friction modifier while ZDDP is more of a anti wear additive. ZDDP would definitely provide more protection for wear in high lift cams and flat tappets.

 

[FCD]

Moly is a friction modifying additive, it is not 100% necessary in an engine oil even though it is said that they reduce engine noise and aid fuel economy etc etc..

ZDDP is an anti wear additive that IS necessary, in a hypothetical scenaria where the boundary lubrication regime breaks down, ZDDP is the last layer of defence, the Phosphorous in the ZDDP reacts to heat in areas of very high friction such as the valvetrain ( on old flat tappet sliding follower engines it is even more critical ).
In a roller valvetrain 600-800ppm of ZDDP is fine
In a non roller valvetrain 1000-1200ppm is what you should be aiming at ( generally speaking, hthe higher the valve spring pressures and the more aggressive the cam profile, the more zddp you need ).

Most motorcycle specific oils for example do not contain friction modifiers as they can cause wet clutches to slip, and yet the engines run fine without Moly or other AW additives, and generally they have high ZDDP levels.

And no, Moly will not affect how the ZDDP bonds to the engine parts.

Your modern Mercedes engine probably does not require high levels of ZDDP, as it's a modern DOHC engine that has much lower valve spring pressures than 60s-70s OHV American V8s in which it generally is a good idea to run a high ZDDP oil.

 

[andrewp1998]

I spoke to Royal Purple customer service about moly and they claimed that they don't add it because it stays in suspension.

 

[aquariuscsm]

Originally Posted By: andrewp1998
I spoke to Royal Purple customer service about moly and they claimed that they don't add it because it stays in suspension.


Their Synerlec street oils had high levels of moly.