I think it's the same with the S 550 (also E 550, SL 550 etc)
It is called S 550 everywhere, but here in Europe, especially in Germany, it is still called S 500 (although it has an 5.5 litres engine now).
The S 280 has a 3.0 litres engine...so they call it S 300 - don't ask for the reason!?
