>Mobil now claims their 15w-50 is now engineered for older vehicles... >It has a lot of ash (1.2%) to prevent ring sticking and oil analysis is showing it be well over 1,200 PPM zinc The problem isn't only zinc, the phosphorus is just as important. that is why the ZDDP additive or oils that have high zinc AND phosphorus. Peter Arakelian - '71 TR6, Daily Driver