2006 Saturn Vue Question: Knocking in engine at start up?

My vue started to get a knock in the engine this past fall as the weather got colder. After a few minutes it stops, I guess when the oil gets up in the motor. A mechanic friend of mine suggested a sea foam fix, but it depends on the motor type. So does a 2006 Vue 4cyl (No AWD) have an over head cam or over head valve engine?
He said to try 'cleaning up' the system with the sea foam motor treatment. There was also some other thing it could be but he needs to hear it to know.