Certified FC-W semi-synthetic vs SN Semi?

[Mainia]

I am wondering how extreme or how much more elevated are these spec vs SN semi synthetic automotive oils for outboard 4 stroke motor oils I know these are two different animals or applications, but I am curious did we gain a massive amount of quality and robustness by buying FC-W outboard oil vs say a Mobil semi-synthetic?

https://www.nmma.org/assets/cabinets/Cabinet456/FC-W%20Combined%20Certification%20Procedure%20Manual%20(3%2016)%201.pdf


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[SuperSalad]

FC-W(Cat) has a base starting point of API SM and the FC-W specification has a base performance level of API SG

Page 22 of NMMA FC-W(Cat)
Page 22 of NMMA FC-W

Quote:
This document verifies that oil is formulated with a core
additive technology that was based on a minimum of API SM performance quality.
Any formulation changes that were made to meet NMMA FC-W Catalyst Compatible®
requirements are not believed to detract from performance in the original API Scategory
tests. Nonetheless, this oil may no longer allow API SM (or higher) quality
claims.

And a similar statement regarding API SG for FC-W.

So, the oils meet the API specs first, then they need to be modified in order to meet the additional corrosion protection requirements of the NMMA specifications.

So by using an NMMA oil you are still getting the same engine performance as the API fluids, but with increased corrosion protection. That is the big gain from using an NMMA certified product over a non-NMMA oil.

Would a non-NMMA oil pass the corrosion tests? Maybe; but you know for certain that the NMMA certified products do.