Why Do Diesel\'s Last Longer Than Gas Engines?
The wash effect you talk about explained for others: 'wash' is when an engine is running in a rich fuel/air mixture regime, some of the fuel sprays on the cylinder walls and dissolves the light film of oil away, exposing it to wear (from metal to metal contact by piston rings) and the combustion flame front.
Someone correct me if I'm wrong, but it's my understanding that in a CDI engine, there simply is no regime which can remotely be considered 'rich.' For the most part, CDI engines (direct injection) run in the lean to ULTRA lean regime, especially at idle (ultra lean), so there is never any diesel not being burned and ending up washing your cylinder oil coating away. Also because of the careful 'swirl' design of the combustion chambers, the flame front is 'cushioned' by an outer wall of cool air, protecting the cylinder walls (and piston crown) from direct flame front exposure most of the time.
IDI engines did this at cold start and under other conditions a little, but diesels have always had less of a problem with wash compared to their gas counterparts (variable fuel mixture ratio of diesel)