M52 520i six 523i six, 528i six to September 1998 may suffer premature bore wear due to high amounts of sulphur in some UK petrol. Solved by replacement block with steel-lined bores on sixes.
yeh watch out for this...my dad has a 728i and it was the same engine and cost him a good few grand to get the new sorted and a new block in. If it had less that 100k miles and was under 6 years old bmw would replace it for free. I think you can phone bmw if you see a car you like and they will tell you if it has had the engine replaced or is going to be effected in the future.
Good cars and they are getting very cheap now
