1995 Cadillac Deville

First have the oil pressure tested with a mechanical gauge. If it is normal, replace the sending unit. If it is low, the oil pump could be worn, the pickup screen could be partially blocked, or the crankshaft and / or connecting rod bearings could be worn. The place to start looking depends on the mileage.

Also be sure the proper oil is being used. Oil that is too low in viscosity will cause low pressure. Switching to a higher viscosity such as 10W-30 will improve oil pressure, but it won't solve the underlying cause of the problem.

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