The only reason I run 20-50 is 30 yrs of using it with no bearing failures. Bearing always look good when torn down. Not saying its right just not changing what has worked for years.
It was good then and good now.
20/50 was the recommended weight oil for performance engines.
Even said so in Ma Mopar's diaries. lol
I use 20/50 in all my old Mopar's.
Never ever a failure, ever. I still have a 383 under the bench that was spun 7500 on a regular basis in the early 80's. I could probably get it running and spin it a few more times. lol
