This is the only info I could find at the moment, It looks like it only pertains to propane or natural gas. You can always give them a call.
Alternative Fuel Vehicle (AFV) Decal
The $0.17 per gallon motor fuel tax does not apply to passenger vehicles, certain buses, or commercial vehicles that are powered by an alternative fuel. The owners or operators of such vehicles are required to pay an annual alternative fuel decal fee as follows (certain restrictions apply):
Gross Vehicle Weight Type of Vehicle Decal Fee
18,000 pounds (lbs.) or less Passenger, School Bus, or Commercial $75
18,000 lbs.-36,000 lbs. Farm or Farming Transportation with an 'F' License Plate $100
18,000 lbs.-36,000 lbs. Passenger-Carrying and Other Motor Vehicles $150
36,000 lbs. or more Farm or Farming Transportation with an 'F' License Plate $250
36,000 lbs. or more All Other Motor Vehicles $1,000
A vehicle that requires an alternative fuel decal may not operate on state highways without a valid decal. No person may fuel an AFV with liquefied petroleum gas (propane) or natural gas unless the vehicle has a valid decal. Motor vehicles licensed as historic vehicles that are powered by alternative fuels are exempt from the motor fuels tax as well as the alternative fuel decal requirement.