How hot does it get?
Does it happen driving in town or on the highway?
If the gauge doesn't get past the half way point it is not getting hot. As far as the oil tell me more about it.
For example does it read low at idle and then go up as you speed up?
Does the temperature of the engine effect the pressure?
When driving or accelerating, the gague will hang between 40-60, usually hovering steady somewhere close to 50.
When idling, the gague fluctuates between 20-35 or so, usually hovering around 30.
There does not seem to be a difference in the pressure fluctuations based on initial startup vs. the engine getting warm. When the engine gets warm, especially during highway driving, this is when my check engine light comes on.