= DIi-DIf+ DIa- DIw
Where:
VD = Volume of detergent.
DIi = Initial detergent inventory of the tank.
DIf = Final detergent inventory of the tank.
DIa = Sum of any additions to detergent inventory.
DIw = Sum of any withdrawals from detergent inventory for purposes other than the additization of gasoline.
40 C.F.R. §1090.1240