Federal Fuel Tax

My understanding is that 400 gallons per quarter of untaxed fuel is exempt from Form 720-
   
  From IRS Publication 510 Definitions-
   
  Blended taxable fuel. This means any taxable fuel produced outside the bulk transfer/terminal system by
  mixing taxable fuel on which excise tax has been imposed and any other liquid on which excise tax has not
  been imposed. This does not include a mixture removed or sold during the calendar quarter if all such
  mixtures removed or sold by the blender contain less than 400 gallons of a liquid on which the tax has not
  been imposed.