From ECI:

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"When we ‘seat’ rings we are really wearing off the peaks of the freshly honed barrel until they become wide enough to carry the load of the piston ring being forced out by the combustion pressure (note the difference between slide A and B). This process can take two hours or 20 hours as there are LOTS of variables, but since you are using new ECI parts and we try to control those variables….I would say the rings seat rather quickly, say within 10 hours. The BREAK-IN period is the first 50 hours and that is the time we allow for the oil consumption to stabilize.
When you have a glazed cylinder (slide C) the oil has oxidized and formed a varnish (mineral oil does this at 400F). The varnish prevents the ring from wearing the peak off the barrel so the rings don’t seat AND the varnish acts like an insulator and does not allow the heat to transfer through the ring to the barrel so it builds up more heat and keeps on glazing. The ring is then hydroplaning on a film of oil instead of contacting the barrel and that extra oil now gets pushed out the exhaust stacks and, if left to sit for awhile (overnight) it would pool in the bottom of the cylinder."