After I filled up my tank last week with regular I ordered the Edge Evolution, which will be delivered to me tomorrow....I still have 3/4 of a tank left....When I install my programmer tomorrow, I'm going to want to use the higher octane setting right away....How much 91 should I have in my tank when I use the higher octane setting????....Should I let the tank with regular get down to empty before I fill with 91?....Or does it really even matter???

 

Run the tank down to at least where the gas light comes on. The program is depending on the higher octane gas and could potentialy cause detonation (which is as bad as it sounds) with the regular octane gas. I know it's a worst case scenario, but really why take the chane?