BMW is considered relatively unreliable, categorized into "hasn't been that much expensive for me so far" tier by Japanese standards. So that's probably not a great counter example.
Fair comment about BMW. So another data point ... Ford also supplied their F150 trucks with plastic oil pans for a number of years. Not sure if that's still the case. But an F150 material decision is going to factor in hard use and reliability. So it's not like this is an insane design decision.
I agree it's suspicious to replace a traditionally metal motor part with plastic, but there's plenty of this history we've gotten past. Consider that people freaked out when intake manifolds started to move to plastic. Now it's quite normal. Even on Japanese motors. The benefits besides cost and weight include the ability to model and mold more complex geometries.
