There is only one fuel company in Canada that offers the 95 Pon (98 Ron) octane rating recommended by BMW as the best for our twin boxers and that is Petro Canada (and Sunoco in the US.) Now, Petro Can. 98 has an additive called Tactrol. Can somebody tell me if this is bad for our engines? I heard the chief mechanic at my dealer's say it was crap and to stay away from it, but I'd like a second opinion. Thank you.