I ran 20/50 racing oil for years and then switched over to half synthetic and half regular racing oil. I would use the weight of oil for how cold it was going to be. Then I mostly ran thin synthetics to gain horsepower from the oil pump not working as hard. Never had bearing problems till early 2010. Motor ran fine, but was getting bearing chips in the pick up screen. Talked to super stock racers, and they are telling me that oil manufactures are talking zinc out of the oil, especially synthetics and it causing bearing wear issues. Some of the super stock racers use a zinc supplement to address the bearing wear issue. Need to talk to stock and super stock racers and get the information first hand. My new motor uses 20/50 and I look for the high zinc content. No problems yet, but it takes a while for it to show up. I normally put a motor together and it stays together for quite a while.
