td5 fuel leakage in engine oil

[defcruiser]

dear friends, i'm new to the forum and wish to submit you a question quite preoccupying to me.
After 10 years with my old 2.5 td 110 I bought in 2003 a new td5 90. I am now at 80.000 km and no problems so far.
But, checking the engine oil this time I noticed something strange: the level rises. I asked a few friends td5 owner and they told me this is common to many td5's an is due to fuel leakage in the engine oil. Actually the oil smells like fuel.
Does anyone know about this? my first consideration is that diesel fuel lubricates as oil and so this might not be a major problem. However how would this affect the engine's longevity?

[Skyview]

I guess you piston rings are not sealing anymore.
I any case it is not good for the engine!