Nice to see that the car is well cared for.
What strikes me is that those good old engines require more oil and more frequent oil changes. Modern turbocharged common rail diesel engines last 30.000 km between oil changes with much less oil. Mine, for example, only has 4 liters. How can such a small amount still guarantee a purifying and lubricating effect after such a long period. Plus the fact that those downsized turbocharged engines are under more stress from higher pressure and faster moving parts.
They say: nothing as reliable as an old diesel engine, but may be also related to a shorter maintenance interval.