Fred,

We just got our IO-550 N back from Barrett Precision Engines.  (For the record, my engine, like yours, was from Performance Engines and also had premature upper ring land wear at about 40 hours TT resulting in ring flutter with large quantities of oil blowing out the breather at a specific manifold pressure.)  I just did not trust the engine considering the problems you, I and others have had so I had a precautionary tear down inspection.  Barrett found a cracked case and one leaking exhaust valve at a total time of about 240 hours. 

So much for the background.  Barrett exchanged the case, honed the ECI cylinders and put in new rings.  I used about 2 quarts of Phillips XC 20-50 in the first hour break-in run at low altitude and high power.  After replacing the 2 quarts,  we flew another 1 hour high power flight with no noticeable oil use.  Then we flew a 3.7 hour leg and a 3.5 leg with no measureable oil use.  I have always run 7 quarts until launching from Austin, TX to Tucson, AZ.  For a little extra insurance I went to 8 quarts.  At the Placerville, CA destination I measured the amount drained for oil and filter change and still had very close to 8 quarts. 

Prior to the Barrett teardown but after new ECI Pistons and Rings were installed, I was getting about 15 hours to a quart.

Steve Colwell   Legacy  Cont. IO-550 N by Barrett