Beginning on July 1, 2017, the Motor Fuel Tax Law, 35 ILCS 505/1, et seq., requires liquefied natural gas (LNG) to be reported using diesel gallon equivalents (DGEs). Fuel distributors are required to sell LNG used as motor fuel in DGEs and to sell compressed natural gas (CNG) used as motor fuel in gasoline gallon equivalents (GGEs). Sales of propane (LP) used as motor fuel shall be in either DGEs or actual measured gallon volumetric units, which are then converted to determine the DGEs that are subject to tax. The Motor Fuel Tax Rate for liquefied natural gas and propane increased to 21.5 cents per DGE on July 1, 2017.
A liquid gallon of LNG weighs 3.5 pounds. A DGE of LNG weighs 6.06 pounds. Therefore, each DGE of LNG reported is equal to 1.7314 liquid gallons of LNG (i.e., 6.06 divided by 3.5 equals 1.7314). A liquid gallon of propane weighs 4.2 pounds. A DGE of propane weighs 6.41 pounds. Therefore, each DGE of propane reported is equal to 1.5262 liquid gallons of propane (i.e., 6.41 divided by 4.2 equals 1.5262).
Informational Bulletin FY 2017-21, Illinois Department of Revenue, June 2017, ¶403-243