What would be more important, would be what oil was used throughout the engine's life. Sludge formation develops over time. The earlier MB approved oils were not suitable for these cars, but even some of the dealers continued to use them. The new oils only came out more recently - they are low ash but also designed for the high temperatures in the exhaust recirc system that can result in decomposition and sludge. (Or so I believe - its been a while since I researched that!)

If an engine flush was done it could be that sludge was dislodged and blocked oil passages? You won't easily find that out!. It does seem to have been a problem with that model and the technology as a whole.

I see you asked about a different engine. Not so easy with all the changes in the computer and wiring required. A CDI engine would be an improvement. Or even a gas engine. But none of that is easy!

__________________
Graham
85 300D,72 350SL, 98 E320, Outback 2.5