Maybe I'm a little slow, but I don't understand the point of this discussion.

Are we trying to determine how long the average 616/617 engine will run without a rebuild? If so, I doubt anyone here knows. I have no idea if more than 50% of the engines make it to 300K. I suspect many of the cars are taken out of service due to other reasons (accident, rust, transmission failure, etc) before the engine gets to 300K.

If we are trying to determine if a well maintained engine can be expected to reach 300K, I think we have plenty of examples here. There will be some variation between individual engines, but I think it's clear that these engines are capable of 300K without major service (I'm also not sure what someone on eBay means by an "engine rebuild").

Are we trying to determine if the average high mileage 616/617 for sale at any given time is capable of 300K? Who knows, I suspect the average "for sale" car is in far worse condition than the cars owned by the people here. Everyone who has spent time shopping for one of these cars knows how much junk is for sale.

I think the reality is that these cars are reaching an age where there are fewer "OK condition" daily drivers around. The cars that have been neglected are either dead or are complete beaters that are probably only good for parts. Most of the well maintained cars are not showing up every day on eBay or at the corner used car lot.

My 300D has just over 300K without any major engine service and is still running very strong. I drive it about 35K per year. It is also not for sale. I suspect that most owners of good high mileage diesels are no trying to sell them. If you are serious about finding a good older diesel, this is a good place to look.

My point is that good high mileage cars do exist and can be found with some patience and effort. I don't think anyone is claiming that each and every MB diesel runs 300K. Lack of maintenance can (and will) kill anything. The older these cars get, the more variation there will be in their condition. However, I am confident that is you gave me a new 616/617 engine today I could drive it well over 300K without major problems.

Good luck.