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?
Since you say this happened after the oil change I am suscpicous that the wrong filter may have been used.
Did you use an oil additive like STP that thickens the oil, or something that claims to clean the engine?
Have the mechanic check the oil pressure with a gauge (not the one on the dashboard). You may have a bad oil pressure sender, which is easy to replace, but if the oil pump is going bad (possible at this mileage) you want to know about it right away.
The oil pressure warning light means the pressure sender is reading ZERO oil pressure, and the engine won’t last very long if that’s what’s really happening.