Why I add 12% (one gallon) of gear lube at every oil change...

[mikkhh]

Looks like that old first generation 3.0tdi just like the I had years ago and ran with 15w40/10w40. Really solid engines actually. Most of them have severely wound back odometers. Nowadays most of them have at least done 300 000 miles. Where I live none of them had SCR. Those engines are cheap on the used market in Europe. You could get used longblock for like 250, complete engines can be had for 500.

I forgot to mention one very important part - are thermosthats working and engine stays at operating temperature? There may be two thermostats presents - one for engine and second for gearbox. If those both are working or replaced and still engine temperature cools down on highway you have to check if there is auxiliary heater present? If yes and it is not working it will also cool down engine in cool weather and also cause extended warm up times and therefore problems with aftertreatment, since the cans have to be up to temperatire FAST.

Make a thread about it. I will chime in.

Since yours is quite old replace oil cooler seals in the V valley. Has the crankshaft damper been replaced? Early 3.0tdi had leaky injector tips as a common issue. Maybe that is the issue why chains get worn out fast on some occasions?

Injectors I check with diagnostics scan tool by looking at injector pressure and time corrections in uS (micro seconds) If there is dripping injectors readings are in like -10 or more. -50 is the official limit but before dripping gets that bad there will be hole in piston already. The long term taught in value can lie if you have swirl flaps issues or soot clogged intake manifold. Values will be zeroed if somebody rewrites injector IMA codes.