I was asked by my sons friend which oil is best for a gm 3.1 in his 96 buick, He is in college and although his parents are paying for school and everything else they won't pay for car care. i told him both mobil 5000 5w30 and supertech 5w30 will pretty much both do a good job and told him i will post it here and ask others what they think and why. I think he is looking for the cheapest decent oil he can find.He will be at school in long island. It will be for the winter i assume.