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Just weekends.

Thank you for the replies. Maybe I will do 5w30 in the winter and 15w40 in the summer next time too .

Hello, I have a 1981 GMC High Sierra with the 4.1L L6 OHV engine. I just changed the oil and put Castrol GTX 10w40 conventional with around 800-900 ppm for zinc. I'm just learning about zinc in oil and flat tappet engines, and was wondering whether the conventional 10w40 was fine or if I'm...