Frequently Asked Questions
Clean Fuel Fleet Program

What is a vehicle's emission certification?
Since the mid-1970's the Clean Air Act has required that all vehicles sold in the United States meet a federal emission standard for three types of pollutants: hydrocarbons, carbon monoxide and nitrogen oxides. The U.S. Environmental Protection Agency is in charge of enforcing the federal emissions certification program. These emission standards have become more stringent over time thanks to improved emission technologies and cleaner burning fuel. The Wisconsin Clean Fuel Fleet Program requires fleets to acquire vehicles that are certified to be lower-polluting since they are certified to standards that are more stringent than those in effect for other vehicles. Vehicles certified to Clean Fuel Fleet standards are over 70% cleaner than vehicles certified to the regular, base federal emission standard.
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What are the Clean Fuel Fleet emission certification standards?
The Clean Fuel Fleet certification standards include all of the following categories:
  • Low Emission Vehicle (LEV),
  • Inherently LEV (ILEV),
  • Ultra-LEV (ULEV), or
  • Zero Emission Vehicle (ZEV)
Each one of these categories pertains to the strictness of the certification standard. The ULEV vehicle is "cleaner" than one certified to a LEV standard.

These standards are assigned to vehicles according to the type of fuel that is used during the certification testing.

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Is the individual fleet responsible for certifying the vehicles for the Clean Fuel Fleet Program?
No. The auto or engine manufacturers have to do the certifying through the U.S. EPA's certification program. A vehicle or engine will have a certified emissions standard when it is available for purchase.

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Are conversions allowed in the program?
Yes. Conversions can be used in the program provided that the conversion system is certified to one of the federal low emissions standards. However, since conversion systems have historically not been required to meet any certification standards, check with the U. S. Environmental Protection Agency to make sure that the specific conversion will comply with the Clean Fuel Fleet Program requirements.

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What is the difference between a "Clean Fuel Vehicle" and an "Alternative Fuel Vehicle"?
A "Clean Fuel Vehicle" is one that meets one of the four federal low-emissions certification standards. The fuel used for certification is the "clean fuel" for that vehicle.

An "Alternative Fuel Vehicle" is a vehicle that operates on a fuel other than gasoline or diesel fuel. Alternative fuels, such as propane, natural gas, ethanol and electricity can be used in a clean fuel vehicles.

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How do you identify a "clean fuel vehicle" that meets Clean Fuel Fleet requirements?
A vehicle or engine comes with an emission label containing the emission standard. The emission label is sometimes called the Vehicle Emission Control Information label or the Important Vehicle Information label. This label is typically located on the underside of the hood or on the cowling in front of the engine. If one of the four certification terms (LEV, ILEV, ULEV or ZLEV) and possibly the words "clean fuel fleet program" appear on the label, the vehicle has been certified and meets program requirements. The wording may differ by manufacturer. If you have any questions about the vehicle certification standard, check with the dealer, leasing company or manufacturer representative.

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What fuels are certified for use in the program?
Fuels are not certified to emission standards -- vehicles and engines are. A fleet subject to the Clean Fuel Fleet Program requirements must acquire vehicles that are certified to one of the federal low-emissions standards. The program is fuel neutral. Any fuel, whether it is natural gas, propane, electricity ethanol, methanol, hydrogen, diesel fuel or gasoline. can be used as long as that fuel was used by the auto or engine manufacturer for the U.S. EPA's certification.

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Can a Clean Fuel Vehicle operate on gasoline or diesel fuel?
Yes. Since a vehicle or engine, not the fuel, is certified to low emissions standards, the manufacturer has the choice of how to meet the certification standards. In engineering a vehicle or engine to meet one of the four clean fuel fleet program certification levels, the manufacturer may rely on engine design, emission control components, on the cleaner burning properties of a fuel or any combination of the three. Recently, changes in engine design and emission control have made it possible for certain gasoline fueled vehicles to achieve a low-emissions certification.

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Where can the state rules for the Clean Fuel Fleet Program be found?
The Wisconsin Clean Fuel Fleet Program rules are codified in chapter NR 487, Wisconsin Administrative Code. For a copy of this chapter, contact:
Wisconsin Department of Natural Resources
  • Southeast Region, Milwaukee -- Jessica Lawent at 414.263.8653 or
  • Bureau of Air Management, Madison -- Muhammed Islam at 608.264.9219

Clean Fuel Fleets

Last Reviewed: January 2006
Next Review: January 2007
Last Revised: Tuesday January 16 2007