Can someone explain why Castrol TWS is sold in liters rather than quarts despite the fact that everyone else seems to sell oil in quarts and that's how a car's oil capacity is typically listed, at least here in the US (and the M3 says "Add 1 quart" when it's low)? Given that a liter is more than a quart, I'm guessing that this is a common cause of all of the overfill stories on here: Tech sees the M3's capacity listed as 9.3 quarts, empties 9.3 bottles of this stuff in there (for 9.3 LITERS), and has thus put 9.
8 QUARTS into the system, or half a quart too much.