Got my new GM 1st gen 350 Rebuilt top to bottom (Long Block). Picked it up and was reading through the papers and they said they recommended using 20w50 Castrol. I was like what. I called and asked they said that yea that was right and that when its warm the oil viscosity will be around the average of 20 to 50 which is around 30 or so. What do you guys think. Its the older 350 gm block. She said it was best but told me I could use 10w30 but recommended 20w50?? Its a well known engine rebuild place will not name names though.What do you guys think?
Using 20w50 Castrol in 1st Gen GM 350?
- Thread starter Josh F
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