AmsOil makes a great 20W50 Full Synthetic Racing Oil that I have used for many years in 440's. I live in the South, with many days of 100+ degree weather, so I prefer the heavier 20/50 blend. New motors need adequate break in on standard oil first, to prevent ring break in problems (AmsOil lowers friction to the point that new rings may not seat). It also cleans up gunk in dirty engines, so a good engine flush should be done first, followed by gasket changes when leaks appear on older engines.