[Wgosma]

F25 motors:
Two choices, N20 4-banger turbo or N55 6 cyl turbo. (2011-2012 model years, which I own avail w/N52 6 cyl non-turbo)

I'd be wary of the 4 banger pre 2015 model year as BMW had problems w/timing chain guide failures - they did not recall but extended warranty to 7 years / 70K miles as I recall. Redesign of guides was done in late 2014 or thereabouts.

I've owned Bimmers for 15 years, DIY a good deal of my service/repairs -purchased 2012 X3 1 1/2 years ago from original owner, 52K miles on clock at purchase, now at 76K miles. Nothing major has 'broken', just replaced the valve cover and oil filter housing gaskets as they began to seep, typical on virtually every BMW. I had shop drain/fill auto trans and xfer case w/new 'lifetime' fluid and reset AWD adaptations, smoother operation noted. I've replaced/flushed the coolant, preventative replaced serpentine belt and belt tensioner/pulley. Remember, I'm running non-turbo 6 motor, so no experience with turbo.

Only somewhat pricey/common repair item I've read about is low mileage failure of (electric) water pumps on turbo 6 motors; it's a $1200+ repair, many posts on forum about failures at 50-70K miles.

I have kept 3 sedans to over 200K, this car I plan to keep to 150K or more - so far it feels like it will go the distance w/proper preventative maintenance as my previous sedans. Change the 'lifetime fluids' as your intending high-mileage ownership, that's a must do in my book.

(I were you, I'd lean towards the turbo 6 motor, BMW's I-6 motors are pretty bullet-proof).

Good luck shopping /Bill