91 Lumina Sedan - 174,000Km
I have a problem with high oil pressure. Once the engine warms up, if I am cruising between 100-120km (60-70mph) @ 2000rpm, my oil gauge reading is way up in the high end sometime touching the 550kp mark(highest mark on gauge). If I'm going up a hill the pressure drops ever so slightly but after cresting the hill (engine now not working as hard) the pressure increases again. The needle also fluctuates a little in the high end from time to time despite being on cruise control and the rpm being constant. I have had the oil and filter changed but still have the problem. This all started when I began using 5w30 synthetic oi during the winter and regular 5w30 for the summer 18 months ago.
Anyone have any ideas?
Andy