what is a 92 Series certified automotive engine?

[Low Class]

I read this in the DD service manual.  It pertains to a thermatic valve located in the top of the oil filter adapter that modulates oil flow to the oil cooler.  The cooler doesn't see full flow 'till 230F.  Says  certified automotive engines had this feature to 1988 when it was deleted.

Does this mean all on-highway engines or was it a California only thing?

[luvrbus]

You will see very few engines with the thermatic valve I haven't seen one in years they have all been replaced  it only lasted for a short time like the 100,000 mile oil change lol

[Low Class]

Thank you sir.  Sometimes the book is confusing.