smartUSA has been using only Mobil 1 0W-40 when they initially change to synthetic oil at the Vehicle Reception Centers (realizing that the cars go from there to various places in the country with widely varing climates). My smart center in Virginia Beach, VA uses 5W-30 with smartUSA's permission, the viscosity most commonly recommended by Mercedes-Benz for smarts worldwide (per M-B Sheet 229.5).
Mobil 1 0W-40 is on M-B's 229.5, is API SM and ACEA A3 grades, but not ILSAC. M1 5W-30 is not on 229.5 (note that the 2008+ smart is Mitsubishi engined, not M-B), is API SM, is ACEA A3/A5, and is ILSAC GF-4.