As a kid I remember a lot of vehicles of the late 40's early 50's vintage followed by a cloud of blue smoke, it was expected of a vehicle with maybe 50,60,000 miles.
I'd be my guess not only oils have improved greatly, but so have engine rings and their designs, as well as crank case ventilation systems
I'd guess todays least rated oils are superior to yesterdays best oils.
I just don't see many valve cover insides caked up like yesteryear and
a properly maintained engine @ 200,000 using little oil if any.
just my $,02
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