Vehicle is our 2005 Mercury Mariner 3.0L V6 at 201K miles. It was bought new, I ran Motorcraft syn blend 5W-20 for the first ~120K miles at 5K OCIs, it developed a valvetrain tick on cylinder 6 (transverse mounted engine, front right cylinder left exhaust valve lash adjuster) at operating temps, so I switched to Mobil-1 High Mileage, then PU which finally stopped the noise, then PPHM or Valvoline synth HM after PU was discontinued. This was when I noticed oil consumption becoming an issue, so I switched to conventional PYBHM 5W-30 this year (2 OCIs thus far) which did not improve consumption. Hot valvetrain tick came back at some point, however it appears intermittently. Problem: Consumes about 1/4 quart every two weeks at ~200 miles of commuting, the drive is 10 miles one way. It leaks a small amount at the front crank seal, possibly the oil pan also...but not nearly enough to account for the volume of oil loss. I replaced the PCV valve with a new Ford piece last year, no change in oil consumption. There were and still are indications of excessive crankcase pressure such as oil residue around the outside of the PCV seal. I verified the PCV tube and vent tube were both unobstructed and no cracks/breaks during the PCV valve change last year. Current fill of PYBHM 5W-30 is at 3,800 miles, I added 16oz of Kreen and ran it up to temp on a vigorous drive. Wife will continue commuting in it, I'll monitor oil consumption as usual, and I'll change the oil at 5K as usual. The other 16oz Kreen will go in at ~2.5K miles on that OCI (unless there's a case to be made for adding it immediately, I'm open to feedback). My thinking is that Kreen treatment will confirm or rule out stuck rings and/or clogged piston oil drain passages. At 201K it's very possible that the rings are just plain worn. No visible oil smoke on cold startup, coasting downhill, or accelerating uphill.