Well I've found its not the type of paste but the amount is important. It's only used as a conduit to get rid of air gap. So less is more kinda thing. The heat sink is still what moves the heat away and the fan cools the heat sink. My lampshade imac was a real good example of this. Lots of heat realated shut downs when new. Took it apart to max the ram and the paste was everywhere, like a overlooked cheese sandwich. Removed it, put a super thin film evenly, not one shut down after.

Sold it years ago to a student.