Hi, have suspected this for a while now but would appreciate your opinions and experience. It's the Z12XEP engine by the way, chain driven.

Hi, bought the car beginning of June and noticed a very very small amount of creamy oil under the filler cap, did some long runs in the car and sure enough the problem went away (I do about 15 miles each way to work and back every day). Most of the time the temp gauge sits ever so slightly below the middle mark, but it does seem to easy to push it above. 2-3 mins or so of idling in trafffic or say a minute of driving uphill doing 30 will cause it to go over the middle mark and it will keep rising until the fan comes on if idling. Is this normal behavior for these engines? As I recall having one a few years back and the temp gauge never fluctuated this much, especially going over 90C when driving along. Also some slight hesitation when accelerating on cold start in the morning. Funny thing is it doesn't use a drop of coolant, can't see a film of oil in the header tank, can't really check if the oil level is going up as the last muppet filled it above the max mark on the last service but oil in the sump is not creamy at all. I'm aware of other issues with this car (cue the typical GM c*** remarks) but not head gaskets. Just wanted to catch it before it does any lasting damage. Thanks in advance for your time and sorry for the essay!