1995 Oldsmobile 88 loosing water intermittently

Some of those 3.8L engines had issues with the intake getting eaten away next to the EGR port. This can cause water consumption without any visible leakage. Also check the water pump weep hole (bottom of pump) for stains or other signs of leakage, Sometimes water pumps will only leak at certain times (when running) so you dont see anything hit the ground. Beyond that, might want to have the system pressure tested to see if it holds