I just purchased a 5 Lt jug of 5W-30 for my son's girlfriends car (2005 3.5 L Malibu with 74,000 kms) because it was on sale. The car, surprisingly, only takes 4 Lts but what I am curious about is the cleaning properties of this oil? Is it just as good as others or is it known not to be as good? I did a small bit of reading after the fact but didn't see anything mentioned about its cleaning capabilities? I would assume some oils are better than others in this dept, but has any of it ever been proven beyond a reasonable doubt?