If there are problems with PCV system and oil is being consumed, basically it’s being fed from the engine back into the intake pipe before entering the combustion chamber and being burnt.
So check the intake plumbing around the throttle bottle for thick oil misted insides and pool of oil within the plumbing. Lightly misted oil insides is probably ok but not ideal.
Ps: I’ve read you shouldn’t push the throttle body fully open by hand and don’t wipe the inside of the throttle body as it may cause high idle afterwards but I’ve got no experience with this issue myself so just an FYI.
^ yep, but looking into the intake system will confirm whether he has oil pooling where it shouldn’t and thus clear any PCV concerns he may have. It’s an easy thing to check and what he asked about.
Then when he is satisfied the PCV system is working as it should be, he can focus on other more probably causes of excessive oil consumption, which as you say is likely due to valve seal seal failure or piston oil control ring failure. For the latter, a compression or leak down test can give a good indication of ring/bore problems and is a good way to get a general feel of engine health.
I do agree that 1 ltr per 4000 kms seems rather excessive and even with revving the crap out of his engine it’s unlikely a bad PCV system will allow so much oil to be consumed via combustion.