I have the greasiest smelliest friend ever, sometimes he smells so bad it actually makes you gag. Loads of people have said stuff to him about it but he insists that he showers regularly which is obviously a lie, his smell isn't BO but nasty unwashed body smell as well. And you just can't get hair as greasy as his if you wash it more than once a week. But he insists that he showers regularly and thinks we are just taking the piss and there isn't a problem. I really don't know what to do about him, if telling him to his face doesn't work then you are actually out of options.