What you did not post (and you know it) is that NMMA does WOT tests in 4S motor ... checks the oil ...and tears down the power head for inspection
Wonder why the HDEO’s don’t just test at NMMA facilities and then rebadge the bottle
It would surely sell for more than 12/gallon ... missed opportunity to double price?
Here is one of the NMMA lube makers ... specs on the link
Exaggerating aside... it has good specs
(Noack etc) that T magic does not blow awayhttps://www.mystiklubes.com/do/product/663095002
That would make up a very small portion of the many types of testing and certs that an HDEO has to meet for the diesel manufacturers.
The HDEO manufacturers don't test and rebadge because:
A: Many NMMA oils have to be catalyst compatible. Some companies are no longer even making a non-catalyst oil. Most HDEO is not marine catalyst compatible.
B: The viscosity specs mostly don't match. Nobody makes a popular 25W-40 or 10W40 HDEO.
C: They generally try to duplicate the OEM formula as closely as possible so as not to appear as a goofy substitute.
D: Some manufacturers like Volvo-Penta literally spec a 15W-40 diesel rated oil as the OEM spec oil for a gasoline engine
E: The diesel manufacturers are just not interested in an immensely transparent marketing scheme.
The part that you forgot to post is that many marine engine manufacturers spec an automotive non-NMMA oil for their gasoline marine engines
Notice which spec Indmar goes by for all of its engines? That's right. API SN. No mention or usage of NMMA spec at all.
We can rehash this all day long, but the fact that straight up 15W-40 HDEO and OTS automotive oil has pushed out so much of the NMMA oils for gasoline marine engine oil is solid evidence that NMMA is about as good as feet on a beluga whale.
We could also get into the NMMA's hilarious adventures in destroying thousands of 2-stroke engines with their arbitrary specifications, to the point that almost every marine engine manufacturer ran away from them and formulates their own 2-stroke engine oils to this very day.