Oil pressure issues

[Mario765]

Hello all,

my D24TIC (engine from 1994) has developed some oil-related problems. It just surpassed 520000km (about 320k miles) so I don't know if it has reached the end of it's lifespan or if there is still hope.
Anyways, the problem I'm running into is low oil pressure and high oil consumption.

The oil consumtion has always been higher and is now at about 1,2l/1000km (600 miles), which I think is acceptable in itself, however, the thing smokes like a freshly-lit campfire, even at moderate throttle and especially on cold startup. This is getting embarrassing in parking lots and at work.

And perhaps more worrying is the fact that now, whenever the engine is warm, the oil pressure light comes on at idle and slightly above idle. Depending on engine temperature, it sometimes flashes or stays lit.

You can also hear the valvetrain getting much louder as it used to be when the engine is warm. Certainly not your normal diesel nailing.

What do you guys think? Could the issue be solved with thicker oil? (I'm currently running 10W40 Motul oil) Or is the engine simply too worn? Also, could the turbocharger be the colperate for the blue smoke, or are the piston rings/valve seals more likely to be defective?

I thought I'd ask here before I take any further steps, too see If it may not be worth the effort.

Btw: The engine is always maintained and has brand new glowplugs, overhauled injectors, new timing belt last year and doesn't leak a drop of oil towards the outside.

Thanks and greetings from Germany,
Mario