I have a 1997 Cadillac Catera. I recently had a used engine (81,000 miles) installed since the old one was bad. I did not install the engine myself, I had the dealership do it. Everything seems to be working fine, except my oil pressure is spiked. At idle the pressure is fine (about 30 psi). As I accelerate the oil pressure shoots up. It maxes the gauge out at about 50 mph. I have noticed that when the car shifts, and the rpms drop, the oil pressure drops simultaneously. And then climbs again as the rpms increase with speed. But again, after about 50 mp it reads 80 psi. The oil light is NOT turning on, and the engine is running quiet, smooth, and at the normal temperature. The only thing I can think is maybe the oil pressure valve is stuck or bad. I just need some input before I bring it in again and sink any more money into it.