That's awesome with the cats not blocking, I run that oil in the Datsun and have in heavily flat tappet cammed 304/355's thinking if it does a cat or two in it's cheaper then wiping a lobe and putting metal through the motor.
Haven't ran it in a car that see's KMs to see if there were any long term issues.
Definitely agree that pressure is a measure of resistance , wasn't to sure how these things flow though. I've heard I don't have to worry about head drains at 7200 rpm so they must keep a good amount in the block and not over fill the top end.
Just did some digging on American sites in 98 they changed it to 10w30 specifications and 2004 it changed to 5w30 but when originally was developed they had 15w40 cold climate 20w50 for 96 and 97.
I'm wondering if they dropped it for cold start noise , keep it aligned with other motors or an emissions thing maybe.
But seems blanket worldwide viscosity change.
I also just found this , guess I'll be able to know exactly what oil to use after I assemble it LOL
Definitely saving this for later!