107C is my highest known oil temp. Not sure what the upper limit of the head gasket, oil or any of the mechanicals could reliably cope with, but I'd say there's a very real risk of boiling your coolant at 120C, especially if the antifreeze concentration is a little low due to a top up with water. My car is running a lot cooler than it was since my first service, 97C max is all I've seen lately. A properly maintained coolant with recommended antifreeze concentration is usually quoted as having a boilingpoint of 130C.