Wandering Oil Pressure Gauge

The car is a 1988 Pontiac 6000 with 210,000 miles on it. When the car is started, the gauge goes all the way to the right. It stays there while driving at highway speed. When I slow down or come to a stop, The gauge goes to the left and the oil light comes on. When I accelerate again, the gauge goes all the way back to the right. The oil has been changed and the levels are fine. Can anyone tell me what is happening. Everything was fine before the oil change although the car had been just sitting for about six months. Am I about to lose an engine?

If the car is running and you’re not getting any kind of noise, and the oil looks relatively clean and at proper levels when checked with the dipstick, I’d say that the problem iw probably either the oil pressure sensor or the gauge itse;f. But being that you’ve got over 200k on the motor, I’d bet it’s the pressure sendding unit/pressure sensor