First of all after…
First of all after rebuilding Ford,Chevy
Pontiac, Chrysler gas engines and many kinds of diesel engines I agree that changing the oil at 500 or less miles is a good idea. Not because of
Big but small metal particles from the break in process however this is not necessarily from tighter tolerances.
In the 30s to the 50s and even the 60s the machining processes were not quite as accurate and piston design and other engine parts improved. More engineering went into piston design than any other part. A piston when cold is oval shaped slightly so that when at operating temperature it fits the cylinder with the proper clearance.
The older the engine the less this is true hence the need for a break in period since the rings were not seated in the cylinder at first. So the sooner you get the metal particles out the better for the engine.
2 more things.
1) every time you run an engine hot the aluminum pistons over expand and get scrape marks from rubbing the cylinder walls, the oil cooks and the bearings don't get lubricated well.
2) Most people fire up their car and take off right away. I have timed at idle and higher Rpm how long it takes oil to get to the rocker arms on an OHV engine at idle. Up to 3 minutes. OHC is quicker. It's like getting out of bed and going to work without breakfast and coffee.
So when you crank up your vehicle, let it run a little bit with no load, if it runs hot shut it off. Don't try to make it home and don't run it low on oil. Some parts like pistons, rings and ohv camshaft are splash lubricated. May be enough oil for oil pump to lube bearings but not other parts depending on engine design.