I am thinking that the tin is coming from the white metal piston big end and
crankshaft support bearings.
You can easily draw your own conclusion what the eventual result will be.
If the bearings are stripping metal, for sure you will soon see a gradual
drop in oil pressure.
They may have been under increased strain from tight piston rings in new
cylinders as you broke in the new Millenniums.
How would your A&P know the bottom end "looked OK" if the bottom end was not
stripped and the parts checked for dimensional wear.
I would keep a very careful eye [and ear] on that engine until it has done
another 25 hours and results of another oil check are to hand.
Good luck with that one !

--
Roy
N5804F - PA28-181

"TripFarmer" wrote in message
...
I just changed the mineral oil after 25 hours with new Superior Millenium
cylinders (standard cast). The rings are broken in and consumption has
stabilized. My analysis came back with high Lead, Chrome, and Nickel
levels which Superior says it normal with these cylinders. However, the
analysis also came back with very high levels of Tin (13.6 vs 1.2 before
the new cylinders). Aviation Laboratories said on the analysis sheet that
this could be caused by bearing wear. My A&P said the lower half of the
engine looked good when he installed the Cylinders. Superior says the Tin
shouldn't be in there from breaking in the cylinders. They suggest
retesting
in another 25 hours.

Anyone know what may be going on with the Tin? Thanks in advance....


Trip Farmer
N8501N
PA28-235