my uncle just got a silverado pickup with the 4.3L V6, and I'm going to be channging the oil. he doesn't want to use a synthetic as I would if it were my new truck, but he also doesn't feel comfortable with going much over 3k miles on the oil even though he drives 3 to 4k a month 95% on the highway. with this type of usage what dino oil would all use? manual says either 5w30 or 10w30, but it's in the 20's around here now so I'm thinking 5w30 would be better? any brand that might work better to stick with?