DEEP: Fuels

Fuels and Energy

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Fuel storage tanks

There are many different types of mobile source fuels in use. Reformulated gasoline (RFG) and diesel are two of the more commonly used fuels in Connecticut. The Federal Clean Air Act (CAA) requires that certain areas that exceed the National Ambient Air Quality Standards for ground level ozone use reformulated gasoline. According to the US Department of Energy, Energy Information Agency glossary, gasoline is a complex mixture of relatively volatile hydrocarbons with or without small quantities of additives, blended to form a fuel suitable for use in spark-ignition engines. RFG is blended to reduce the emissions of volatile organic compounds (VOCs), nitrogen oxides, and toxics from motor vehicles. RFG is enhanced with fuel additives.

Oxygenates are fuel additives that are put into fuel to reduce harmful air pollution.  The two most commonly used oxygenates are Methyl Tertiary Butyl Ether (MTBE) and ethanol. The use of RFG containing MTBE was banned in Connecticut, on January 1, 2004. Connecticut currently uses approximately 1.5 billion gallons of RFG containing ethanol on an annual basis. For more information on Ethanol please see the links below.

On-road diesel fuel, also known as highway diesel fuel, is intended for use in some passenger cars and heavy duty trucks. According to the US Department of Energy, Energy Information Agency glossary, diesel fuel is a fuel composed of distillates obtained in petroleum refining operation or blends of such distillates with residual oil used in motor vehicles. The boiling point and specific gravity are higher for diesel fuels than for gasoline. Highway diesel fuel is regulated by the EPA to establish low sulfur requirements to assure healthy air quality.

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Ultra-Low Sulfur Diesel (ULSD) fuel is a cleaner burning fuel that contains a maximum 15 parts-per-million (ppm) sulfur. Some chemical characteristics and natural impurities in diesel fuel can affect exhaust emissions from diesel engines, damage or impede the operation of emission control devices, and can increase secondary pollutant formation in the atmosphere.

Non-Road Diesel fuel is intended for locomotive, marine and non-road engines and equipment such as farm or construction equipment that must meet the Low Sulfur Diesel fuel maximum of 500 ppm sulfur. EPA has amended its regulations to make the standard 15 ppm sulfur effective in 2010.

Some vehicles are also designed to use renewable or alternative fuels.  Renewable Fuels, such as biofuels, are fuels that are produced from renewable processes. The EPA regulates renewable fuels under the Energy Policy Act of 2005 (EPAct) and the Energy Independence and Security Act of 2007 (EISA). Alternative fuels are non conventional fuels such as biodiesel or hydrogen.

The federal government also regulates fuel economy.  Fuel economy is the amount of fuel used by a vehicle to travel a certain distance. Fuel economy standards are best recognized as the city and highway driving miles per gallon (MPG) ratings seen on the new car stickers of all new cars.

The use of fossil-based fuels has large implications for climate and air quality conditions.  Approximately 70% of Connecticut’s energy is derived from fossil fuels. The combustion of fossil fuels releases air pollutants and greenhouse gases, which both endanger public health and the environment as well as contribute to global climate change. For more information, go to the DEEP's energy website

Related Information

Analysis of the Use of Ethanol as a Fuel Additive (Final EtOH Report January 2, 2007) (PDF)

Public Act No. 07-4, Section 35: Report on Alternative Fuels (PDF, 14 MB)

DEP comments on proposed Corporate Average Fuel Economy (CAFE) standards for light duty trucks model years 2008 through 2011 (PDF)

New gas cans sold in Connecticut must be Spill-Proof Gas Cans that have been designed to prevent leaks, limit spills and control the release of these vapors that are harmful to your health and contribute to ground-level ozone.

Stage I, Stage II, and Onboard Refueling Vapor Recovery systems prevent the discharge to the atmosphere of gasoline vapors from the loading of gasoline into underground storage tanks (USTs) and the refueling of a motor vehicle’s fuel tank.

Historical Connecticut Fuel Waivers

Content Last Updated on January 31, 2017