I have an old 1987 V8 Holden. It has low kms on it (120,000) but unfortunately, was not been well maintained by its previous owner When I bought it, the oil looked ok and the engine was quiet. However, when I changed the filter, it was filled with grit and looked like it hadn't been changed in ages. I am guessing it had been used to filter oil that had been overused Not long after, the pressure relief valve clogged up and caused zero oil pressure Anyway, frequent changes now have inevitably uncovered some valve noises (either from blocked oil passages or wear) and a rather alarming noise from the engine at startup in the 3 sec before the oil pressure rises at startup. It blows no smoke. I have been running dino 20W - 50 since there seems to be no Australian synthetic which is similar to this spec and this is what the engine is meant to use. I am thinking it couldn't hurt trying Mobil 1 5 - 50. Thoughts ?