washdown has not occurred here, maybe because of the climate
however I have seen diesel in engine oil a time or two usually from mechanical failure of some sort, and utter carelessness in regards to oil changes. Hey the book says 200 hours first time right? So that means I can probably go 400 hours. Oh, since I have synthetic, I can run 2000 hours on an oil change.
perhaps washdown is a function of regeneration, dunno. It wasn't discussed at any of the classes I was forced to go to. Oil quality was a big deal as was keeping the air filter clean. The biggest issue in reference to common rail was moisture and/or gasoline in the fuel. Eats supply pumps and injectors. Almost nobody checks the separator and almost everyone uses the cheapest oldest dyed fuel they can find which sits in the tanks for up to a year, picks up moisture (condensation) and is suspended in the fuel. Then it eats injectors and supply pumps; yet the owner can't figure out why. A fuel chemical analysis almost always shows water and/or gasoline, and if this happens....kubota ain't gonna warranty it. It ain't their problem the fuel's got water in it. And if it aint all flushed out and done properly, it'll happen again. Common rail stuff is extremely sensitive.
the downside to common rail, dpf, and/or def is just like diesel pickup trucks. Maintenance. You ain't ignoring it now like you could with the old stuff. Or, I guess you can but it's likely to bite you in the backside later on. And secondly, there is more maintenance that has to be done, so it costs more. That'a an unfortunate side effect of having to deal with it.