Almost all of the full or part syn are Dexos. 2009-2010 they started including the Dexos recommendation on the oil cap. They also changed the ATF recommendation to Dexron VI, which is a synthetic.

 

Look for evidence, spots on ground etc. Is your tailpipe oily at bottom end ?

 

Look at the front cover crankshaft seal, the valve cover, the oil pressure sensor and the oil filter cap area for oil .
I also suggest have a look at the throttle body , oil can get sucked out of the PCV hose down to the rubber elbow at the throttle body.