I spoke with Dennis today and confirmed that gasoline will only be tested after someone has made their second, or back up qualifying run. They will take care of that the in the impound area along with the other record certification procedures. So you can have the gas already in the vehicle when you arrive for the event, and add more as needed.
For additional information, I received the following regarding VP gasolines and their DC testing values.
VP 110 - DC Neg 1.20
VP C12 - DC Neg 0.40
VP C14 - DC Neg 1.40
VP C16 - DC 0.00
VP MS100 - DC Pos 13.00