(1) Except as otherwise provided by the commissioner, or by firmly established trade custom and practice: Commodities in liquid form shall be sold by liquid measure or by weight; and
(2) Commodities not in liquid form shall be sold by weight, by measure, or by count.
(3) The method of sale shall provide accurate and adequate quantity information that permits the buyer to make price and quantity comparisons. The commissioner may issue such reasonable regulations as are necessary to assure that amounts of commodity sold are determined in accordance with good commercial practices and are so determined and represented as accurate and informative to all parties at interest.
(4) Natural gas motor fuels shall be sold as follows: Liquefied natural gas motor fuel shall be sold in diesel gallon equivalents; and
(5) Compressed natural gas motor fuel shall be sold in gasoline gallon equivalents or diesel gallon equivalents.
(6) The commissioner shall promulgate reasonable rules as are necessary to establish conversion units from mass to gasoline gallon equivalents and from mass to diesel gallon equivalents. Such rules shall be promulgated in accordance with the Uniform Administrative Procedures Act, compiled in title 4, chapter 5.