When you change the tune of your car, from 87 to 91, do you run the car down to empty then fill it up to 91 right before you put in the new tune? Or do you fill it up a at least 2of times with 91 to try and get rid of the 87 as much as possible then add the tune?

 

Run it down as far as you can get it. If your running a supercharger you should refil it like 2 times before the tune.