Outside of some catastrophic failure, as long as the body is good (I live in the rust belt) I don’t care about milage. I’ve had a few 200k+ BMW’s of varying years. Most notably a 135 and 328xi F31, and numerous other non-BMW vehicles over 200k. However I used to be an auto tech and do all my own maintenance and repair, so that cuts down on any huge costs.

The turbos… mainly.

Direct injection is more efficient too. Combine that with tuning and stock motors can instantly make noticeably more power, IE N54/55.