As a result of the 1977 amendments to the Clean Air Act (CAA), Missoula was designated nonattainment for carbon monoxide (CO) by the U.S. Environmental Protection Agency (EPA) in the Federal Register (FR) notice (43 FR 9010) on March 3, 1978.  The National Ambient Air Quality Standard (NAAQS) for CO is 9 parts per million (ppm) for an 8-hour average concentration, not to be exceeded more than once per calendar year.  Missoula’s violations of the CO NAAQS were attributed primarily to motor vehicle emissions and residential wood combustion.  The community took several steps to reduce the ambient levels of CO, including reconfiguring traffic intersections to relieve congestion and implementing rules to limit emissions from residential wood combustion and outdoor burning.  Missoula continued to violate the NAAQS until the early 1990s.   

Following the promulgation of the Clean Air Act Amendments of 1990, EPA classified Missoula as a moderate nonattainment area for CO (56 FR 56694) based on a design value of 9.7 for 1987 through 1989.  This designation required Missoula to develop a new base year inventory for 1990 and establish an oxygenated fuel program by November 1992.  In June 1992, Missoula incorporated an oxygenated fuels program into the Missoula City-County Air Pollution Control Program.  It was approved by the Montana Board of Environmental Review (BER) in September 1992, and implemented that November.  On November 6, 1992, the Governor of Montana submitted the oxygenated fuels program to EPA for approval.  Since implementing the oxygenated fuels program, Missoula has not violated the CO NAAQS. 

The oxygenated fuel season runs November 1 through the end of February of each winter.  During this season, all gasoline used to fuel motor vehicles within the control area must be oxygenated. 

What is carbon monoxide?

Carbon monoxide (CO) is a clear, odorless gas emitted by inefficient combustion of any type of fuel. It interferes with the body's ability to carry oxygen in the bloodstream from the lungs to all parts of the body. Low levels of CO in the bloodstream can cause headaches, loss of concentration, and slowed reaction time. At higher concentrations it can be life threatening, especially for expectant mothers and small children, and people with asthma, emphysema, or circulatory problems. Even healthy people who are exercising on high pollution days can also be adversely affected.

What is ethanol?

Ethanol intended for fuel is usually produced from grains such as corn, wheat, and barley, and results from a fermentation process. About two and a half gallons of ethanol can be produced from each bushel of corn. A by-product of the process is used as cattle feed. When it is added to gasoline at the concentration of 8% by volume, it will increase the octane level by about 2 points. So if the octane rating listed on the gas pump is 87, gasoline containing ethanol will have an octane rating of about 89, which results in the equivalent of a premium grade of gasoline.

How will oxygenated fuel affect vehicle performance?

Because the addition of oxygenates to gasoline increases the octane rating of gasoline, vehicle performance will generally increase somewhat. Because the performance increases, gas mileage may drop but usually only by less than two percent. Cold temperatures and wintertime driving conditions tend to lower gas mileage by more than this amount.

Will using oxygenated fuels void the vehicle warranty?

No, all major vehicle manufacturers warranties remain in effect when using fuels oxygenated with ethanol. In fact some manufacturers recommend using higher octane fuels to obtain the performance characteristics the engine was designed for. Some manufacturers caution against using methanol or wood alcohol as a fuel additive because of its corrosive nature. No gasoline blender in Missoula will be using methanol as an oxygenate.

How will oxygenated fuel affect older vehicles?

Older vehicles, especially pre-1975 models, may have parts such as gaskets with elastomers, which are more susceptible to swelling or degradation when using alcohols and ethers in gas. These parts are also affected by other aromatic compounds added to gas in recent years because of the lead phase-out in gasoline. All of today's gasoline, with or without oxygenates, is generally more aggressive towards fuel system materials than it was 10 to 15 years ago.

What about ethanol and filter plugging?

Ethanol can act as a solvent for contaminants that often build up in gasoline tanks. The gas station may need to change the pump filter after the first load of fuel has been delivered and the same may be true after your vehicle's first tank full of ethanol gasoline. After that, fuel filters will not have to be changed more often than is recommended by the vehicle manufacturer. The cleansing effect of ethanol will be beneficial for removing deposits and keeping carburetors and fuel injectors free from dirt and deposits.

What about water separating out of the gasoline?

When ethanol is blended with gasoline and used in small engines, water absorbed from the outside air can cause the ethanol and water mixture to separate from the gas and sink to the bottom of the gas tank. This should not be a problem unless gas is stored for a long period of time where it has the ability to absorb water to over half a percent. To help avoid condensation of water in gasoline that is stored, use containers with tight fitting caps. Gasoline should not be used if it has been allowed to sit for extended periods of time. Because ethanol has the ability to absorb water, consumers will not need to add gas line antifreeze to their gas tanks in order to prevent fuel line plugging due to ice crystal formation.

What about the use of oxygenated fuels in small specialty engines?

Engines found in chain saws, snowmobiles, powerboat engines, etc. may have elastomers, which are more susceptible to degradation when alcohols and ethers are used in gas. When in doubt consult the engine manufacturer. In 1988 tests were done on chain saws, weed trimmers, portable generators, blower/vacs, lawn mowers, and water transfer pumps from seven different manufacturers using a 10% ethanol blend of fuel. After more than 1,300 hours of operation to simulate four to five seasons of use, not one failure occurred. The engines were disassembled, inspected, and compared to engines that used unleaded fuel. The test authors noted that no service or repairs (beyond the manufacturer's recommendation) were necessary. Evinrude, Tecumseh, Sears, Briggs & Stratton, and Ski-doo Snowmobiles have all indicated that gasoline blended with ethanol is suitable for use in their products.