So overall what is the best oil to use a a gas vehicle? I have two vehicles a 2004 dodge ram 1500 quad cab withe the 4.7 lt V8 and also a 2004 Pontiac grand am Se 4cylinder. The pontiac is my Fiance and she gets her oil done at walmart and they put penzoil in it. Is that stuff really not good for motors. My truck I just bought so I dont know what brand of oil the dealer put in her. I do know they change it before I got it. It says in the owner manual to only use SAE 5w-30 is that true as well? Any help would be appreciated. Truck has 63,400 miles on it and car has 70,000 miles on it.