I hate to say this, but the oil pumps in many Cadillac engines are like tinker toys. If you ever saw one out of the box, you would know what I mean. The oil pressure relief valve, which is part of the oil pump, might be clogging up from sludge. You MUST use Mobil One in these engines. ELF oil is acceptable also, but only if it meets the specifications listed in your owner's manual. READ your owner's manual oil specifications section. Another thing that can cause this is a low idle speed. If the idle is too low, it can cause the oil pressure to drop, as well. Clean you throttle body, plate, and IDLE AIR CONTROL VALVE with Amzoil Foaming Cleaner. It is hard to find, but worth it. Do this with engine off, at first. Then with engine running full HOT. Use the spray to clean your PCV valve, as well. Use Seafoam or Amzoil crankcase cleaner to remove varnish and sludge that may be inside the oil passageways. Idle the engine for 20-30 minutes. THe penetrant in these cleaners should restore your oil pressure relief valve to good working order. Drian the oil and use the prescribed oils. Your oil pressure should now be stable and the chime should not sound. Have you been using the WRONG OIL all along????? READ your manual 4-5 times and believe what you read. Best of luck to ya'.
