It sounds like he bought the Syntec in the black bottle, typically found at Autozone. That oil is certified against MBz 229.3.

Per API spec, an xW-40 oil must have a certain viscosity within the designated range. Many seem to be totally lost on what the xW portion of the label really means...it indicates how easily an engine will turn at low temps relative to another oil. A cold crank simulator and rotary viscometer are used to determine an oil's xW rating.

Remember: