Quote from that mechanic
Negligable wear on all components.
Piston to bore clearance:
#1 - .0012", nil taper, .002" out of round
#2 - .0005", .0008" taper, nil out of round
#3 - .0007", .0008" taper, nil out of round
#4 - .0005", .0005" taper, .0004" out of round
Bores glazed, staining on pistons indicates poor oil & 2nd ring seal, staining on intake ports indicates excessive blowby.
Heavy carbon deposits on piston crowns, head chambers & valves, valve seats pitted by trapped carbon.
Valve guide clearance:
Intake - .002"
Exhaust - .0025-.0027" (!!)
Stain trails from guides indicates oil leakage, nil measurable wear on guides or valve stems.
In short - rings are too ****ing thin & cannot control the oil in a boxer engine, oil getting past the stupidly low tension thin oil rings prevents 2nd & top rings from bedding & glazes the bores, excessive blowby then occurs blowing oil out the PCV system into the intake runners. All this is compounded by very loose valve guides failing to control the oil.
They learned nothing from the EJxx engines issues."
This scares me..... This is the same sort of issue my local mechanic was talking about except he didn't know was the "exact" cause because he got one at an auction and sold it. Other than that...Subaru needs to look at that thread.