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I was on my way back from MN this past weekend and oil pressure dipped to 50 psi 1.45hrs into the flight. I departed with 6.25 qts and landed with 3.75 with lots of oil on the belly behind the breather tube. I stopped short of home and left it at a reputable shop at KARR. Their service manager emailed me yesterday morning with not-so good news. Note: I replaced cylinder #4 1.5 years ago and the engine has approx 1450 hrs on it. Opinions, comments, and suggestions for my next step (s) greatly appreciated! Brian, We finally had a chance to look at your engine first thing this morning. This is what we see.Engine only had 3 quarts of oil in it by the dip stick before starting anything. This would start causing a low oil pressure condition with the oil being that low. No external oil leaks to speak of .Borescope inspection found cylinder walls pitted from corrosion, scoring in several cylinders, #3 has some nice ones, cylinders have no honing marks remaining and are polished where not corroded. Large amounts of carbon on the pistons from oil burning. Large amounts of oil puddle in the cylinders.Ran the engine to temp after adding 1 quart for the run. Runs not bad, temps look good, sounds good.Compression check hot #1-57, #2-78, #3-77 and #4-73 all over 80. Compression is a misleading due to the amount of oil in the cylinders is sealing the pistons to cylinder walls.We did a pull thru test turning the engine slowly and two cylinders do not hold compression at all, almost no compression.Cut open the oil filter and once again not too bad, but some aluminum and ferrous particles, lots of carbon. My concern would be the scoring. What has been in these cylinders. Looks like you have at least three cylinders, but #4 which has been off doesn’t look any better have lost total oil control. Corrosion pitting will cause this along with it accelerates ware on the rings. I would recommend removing two cylinders, look inside the engine and check the cam and lifters. Review logs and if all looks good remove the other two cylinders and have all four reworked if possible. They may need to be over bored +.010 to .015 to remove the corrosion and get them back into correct bore shape. If inspection finds chipping or spawling of the lifters (which could be the cause of the scoring we see in the cylinder walls) would lead thing into a different direction since the only way to remove Lycoming T lifters is to split the crankcase.Is it possible to get copies of the engine logs sent to me. I believe you said it has about 1500 hours on it since overhaul. Thank you and let me know what you think and would like to do.