You can get Mobil 1 0W-40 at just about every Walmart. I hav eye to see anyone selling 10W-40 synthetic. You can get 5W-40 from Vavoline. The trick is to find someone selling it. Around here I can only get through a local NAPA auto parts store. I was using this oil in my VW Passat. The owner's manual for that car clearly states to only use xxW-30 oils in the case of adding, not for full oil changes. I don't know of any European car that calls for anything less than xxW-40. I haven't found out why, but all European cars call for the "thick stuff".

__________________
1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member