i think yor mechanic needs his head examined.
i'm the agent for petromin in ISB & RWP and i can assure you that most of the oils in the same class as HX7 are good. My suggestion is that you go for any brand you wish, just make sure the oil is up to spec with the current APi certifications and that the SAE rating is suited for our environment. 10W40, 20W50 etc are ideal.
obviously i'll suggest Petromin Ultra7 as well but ultimately the choice is yours so i'd suggest you do your research before changing an oil you are already comfortable with.