RPO587,,, Since this is a general question, I dont think I can get in too much trouble. Simple answer------When I was 19 yrs old I started using Valvoline 30 wt. Have never changed, after seeing under intake during cam change after many miles. 58 yrs old now and am still using it. I dont think it is one iota better than any other major brand, but when I find a product I am happy with, I stay with it. As far as weight--- 30 wt works well in this part of the country, and again, have never found a reason to change.