I was doing a final demonstration acceptance flight of a 1974 C182 (4800TT 300tfrm on Superior FRM millenium cylinders L-470-U) cylinders and encountered the following oil pressure anomolies:

Owner flew plane to my home airport, about an hour, he, an instructor, and I then flew for 1/2 hr with owner piloting, we landed, I took over controls, owner in rear seat, flew another 1/2hr+, then landed, shut down, let owner out and instructor and I were going to fly w/o owner for final checkout.

1. Upon restart (only a couple of minutes after shut down), oil pressure would not come up to green arc at standard idle (900-1000rpm), came up to green at 12-1500, but came back down when RPM's reduced.  We shut down, consulted owner, he said he had never experienced this anomoly, but rarley, if ever, did a hot restart.  Checked oil, found to be at or slightly below 8qrts (12 qrt sump, usually runs 8-10).  After adding oil, oil pressure was in green arc immediately upon start up (engine had probably been off for 1/2hr).  Instructor and I flew for 30-45 minutes, all engine parameters normal (plane has original Cessna analog gauges and EDM700 engine monitor (installed w/ reman engine).  Just before shut down after this flight, I noted oil pressure was at or in red (<10psi), not sure what RPM was (probably 6-700rpm), but pressure returned to green arc immediately upon increasing RPM to 1000RPM.  Owner talked to his A&P who indicated that it was probably a gauge or probe issue.

2.  Plane just came out of annual a couple of weeks ago and flown only 3-6 hrs since.  Owner says he showed 10qrts of oil on dipstick before flying down for inspection.  A&P not sure how much oil was put in at annual, says they use bulk and don't accurately measure, also noted that new oil filter takes almost a quart.  Owner also has flight logs that indicate little or no oil added between 30-35 hour oil changes over the last 6 months.  Any comments on what the oil retention of a 470-U is when hot versus cold?

3.  One of the cylinders showed a 66/80 compression, all other firmly in the 70's.  (300 hrs on reman) Should this be a concern? Engine has a 5 year warranty which is transferrable.

Have to decide whether to buy or not soon.