0W-30 isn't on the MBUSA approved list but is on the DB list from Germany! SO don't worry! Shouldn't cause any problem at all.
On MBUSA chart 0W-30 can be used any time that 5W-30 is used.
MANY new cars are using only 5W-20 oil year round, even in the hottest weather.
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)