Just got my Celica a couple months ago and I just read in this post that the gts uses premium gas... I've been pumping 87 or whatever button has the 7. Did I screw up big time? Is premium the button on the far right? I think it goes 87-89-91. Is it too late to switch. Idk if previous owner uses premium too so it might be more than a couple of months. Maybe years.