[tricky]

Not all N series engines are awful. The N52, while not as amazing as the previous M52/M54 engines, is a fantastic, reliable engine. However, the 4 cylinder N20 used between 2011-2017 is the worst. Faulty timing chain guides often fail and immediately grenade the engine. They were so bad there was even a class action lawsuit

[avar]

The N53 is even better, BMW phased out the N52 in favor of it, except in developing economies with subpar fuel standards.

[tom_]

The N53 is notably one of bmw's less reliable engines. Everything that goes wrong with it is tedious to debug and ends up hugely expensive to fix because you always end up needing to replace several pricey injectors. Then it breaks again later.

The N52 seems rather better, as all its common faults are relatively cheap to fix.

[michalf6]

Yup, they switched to piezoelectric injectors in N53 which are crazy expensive and regularly fail.