GM recommends Mobil 1 0w-50 for their 632 crate engines. The owner is used to running 20w-50 in his race engines. I tell the guy to run what the GM engineers tell him to run but he isn't super comfortable with it.
That's what I have been running for a few years now. I run alky. If a lot of racers installed oil temp gauges and actually seen how hot the oil really gets they wouldn't be running syrup for oil.
