Is name brand oil, (castrol, valvoline, pennzoil,...) that meets required specs, (dexos..) basically going to give the same results for basic passenger car driving, within a category (synthetic, synthetic blend and conventional),? I was going to ask if they were the same but I know every manufacture has an additive here or there that is proprietary so I just stuck with the idea of, gives the same results. I went to walmart and had pennzoil, castrol, and valvoline in my hand and was wondering if it makes any difference to pick one or the other. I change conventional at 3,000 and synthetic at 5,000 and unless told otherwise think major label oil will all work just as well.