Why Moly in marine gear oils?

[friendly_jacek]

I always used blue Mercruiser high performance gear oil for my alpha2 sterndrive. There are lots of discussions on the forums arguing why or why not use the required Merc/Quicksilver lubes. Most often it's argued that those are full synthetic lubes with high additives levels. I never bought the synthetic claim based on the evidence how easily they sludged and my review of MSDS clearly stating petroleum oils.

However, just recently, I found those lubes are indeed special by finding VOA posted by our own Bobistheoilguy back in 2003: http://www.bobistheoilguy.com/forums/ubb...6798#Post706798

They contain Mo additive in addition to P and Ca. Not sure if B was tested. I don't see Mo in typical gear oils.

Here is the question: what is the function of Mo in marine gear oils and why typical car gear oils don't use it?

Thanks!

 

[Food Scientist]

Moly is used in quite a few gear lubes, Schaeffer's being one company that has used them for quite a while. The moly is used to reduce friction as the coefficient of friction of moly is very low and it is oil soluble depending on the type of moly used.

 

[friendly_jacek]

I knew about Schaeffer's. I was curious why most gear oils don't use moly. Is it because EP requirements of GL-5 can be easily satisfied just with cheap Phosphorus and Sulfur? Or is it because they contain Boron now?

 

[Food Scientist]

Yes, the GL-5 requirements can be satisfied with phosporus and sulfur and that is how most companies do it. Boron is just another friction modifier such as moly, just not as good IMO.

 

[friendly_jacek]

I think B is EP agent and not just friction modifier. Not sure about the Mo vs B superiority. All I know is B almost replaced Mo in engine oils by now.

 

[MolaKule]

Quote:
Here is the question: what is the function of Mo in marine gear oils and why typical car gear oils don't use it?



MoDTC is a multifunctional addtive which is an Antioxidant, Antiwear/Antiscuff, Friction Reducer, and an Extreme Pressure agent.

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=530321#Post530321

 

[friendly_jacek]

Thanks. I understand what Moly is. The question was rather why in high performance marine oils and not automotive gear oils.

 

[Food Scientist]

It is available in automotive gear oils, which is why I mentioned Schaeffer's. Most companies probably don't use it because of value, as the perceived benefit versus cost doesn't pencil out.

 

[MarkTaylor]

Moly Universal Gear Lube uses the Soluble Moly in order to resist oxidation and thermal stress which is operating at temperatures 105°F to 145°F higher than conventional gear lubricants.