When I first got my car three years ago, I was planning to start using normal petrol (I used premium for my old Zen earlier), but thanks to habit -- I told the pump attendant to put premium! I've been using premium all this while and now, for obvious reasons, would like to shift to normal. I found a thread there for diesel engines that suggested using normal. Does the same hold true for petrol engines as well? Is there a risk in moving from premium to normal petrol now? If I do make the shift, do I need to drain my engine of any premium petrol or a little mix won't be damaging? I assume since it is octane and additives anyway, it isn't going to make a difference if a liter or so of premium is mixed with 20 liters of normal -- any thoughts?