400,000km is only about 250,000 miles. With absolutely minimal maintenance 250,000 miles is a cake walk for any MB I've ever seen, even a carbureted one. For that matter most of the mainstream Toyotas of today will do this. Toyota IMHO is the best Jap car for long term durability and reliability. My wifes 4Runner is running up on to 150,000 miles with an absolute minimum of trouble along the way. In fact the only problem that I can lay off on Toyota is that the expansion valve closed up. It cost about $40, plus some 134, some oil and about an hour and a half to replace in the driveway. Now that is minimal corrective maintenance for 150,000 miles. Even with that track record, however, it doesn't approach a 240D.
Even with the current models, most any MB's will go 250,000 miles albeit with some failures of the gadgetry. The Lexus gadgetry will be no difference.
Have a great day,