Thanks Tim this was the info I was looking for. It had never occurred to me to question the major band name oils I had been using in my engines. I have always used Pennzoil exclusively but I am in the process of an engine build up which includes a new flat tappet cam, lifters and new higher strength springs. So when I came across the message about oil formulations I felt best if I go to an area visited by persons knowledgeable in lubrication. Once again thanks for the info.