Has the undyed diesel tax rate increased? Yes. Beginning July 1, 2017, the undyed diesel tax rate is increased to 21 cents. See important notice 17-08 for rate increases for subsequent years. May 10, 2017 19:26 Related articles Has the compressed natural gas tax rate increased? What qualifies for a Tennessee agricultural exemption? Has the undyed diesel tax rate increased? Who is entitled to the tare allowance for motor fuel taxes? Can an unlicensed exporter of petroleum products receive a refund for privilege taxes paid on the export of its products?