When idling the engine oil pressure can be as low as 15 to 20 PSI until the engine warms up especially during cold weather.
Then sometimes the oil pressure may be as high as 45 to 55 PSI when idling or when going down the road at slower speeds.
When on highway driving speeds the oil pressure can be between 55 to 65 PSI and sometimes as high as 75 PSI.
If the oil pressure gets above 75 PSI and stays above that oil pressure reading then it could be caused by a pressure relief valve not working properly.
The oil pressure relief valve is responsible for preventing the engines oil pressure from getting to high and when it doesn't work the engines oil pressure keeps rising which can lead to oil seals leaking and cause other damage to the engine.
So if your engine oil pressure stays high you should get the engine checked out by a mechanic before your engine gets damaged.
The cause of the engine oil pressure being high can also be caused by a bad oil pressure sensor or even dirty oil or clogged oil filter.
If you haven't changed your engine oil after 3,000 miles or haven't changed your oil filter either then it could be as simple as that.