My 190e 1987 was hit in parking lot minimal damage to front right bumper and light assem from suv backing up. I had the car towed to a collision repair center. However, after leaving, the pressure gauge was on zero when noticed about 4 miles out. I then heard lifters and shut car off. I then had car towed home. I took oil filter off and started car , did have pressure. i then placed filter back and pressure went to 3 at idle. However after 10 minutes, the lifters started I belive there are 16 on this car making a noise and then after 5 minutes stoped. The odd part is that the suv could not have hit my benze that hard because radia ok, fan ok, I then noticed as engine warmed up, the pressure started to drop and at 2000 rpms idle the pressure was at 1.7 and I shut engine off. Is this engine gone? I did not hear knocking sound at bottom part of engine rods. just lifters. Have not checked oil for metal or cut filter in half to check for metal. please advice?????

Thank You
in advance because this type of advice does not come cheap .