I've just had a 60,000km service and all is well. The mechanic showed me that the crankcase breather is depositing some oil in the inlet manifold which will carbonise and restrict airflow and so economy/power. He said this is normal in all diesels of this type and advised me to fit an oil separator (around $200) and drill a hole in the sump to drain back the oil. He has done this to his Land Cruiser and said it gives extra power etc. The other option is to use a spray release in the manifold occasionally. I have known him for 20 years and he is a straight shooter. Does anyone have actual knowledge (no guesses or rambles please) of this. (It did actually have more power and flexibility after this service, which I did not expect.
Cheers
Bob H