Hobbies And Interests
Sulfur Additives
The EPA's diesel additive regulations emphasize safe levels of sulfur to improve public health. The 15 parts per million Ultra Low Sulfur Diesel specification phased in from 2006 to 2010 improved sulfur concentrations in diesel drastically, decreasing exhaust emissions of sulfur by more than 90 percent according to the EPA. Low and Ultra-Low Sulfur Diesel fuel, already introduced into highway diesel, is being introduced for off-road, non-road, marine, and locomotive engines between 2007 and 2014. Exceptions to these specifications exist for certain marine vessels but cap sulfur content at 1,000 parts per million for even these vessels, unless operators find other ways to arrive at similar levels of emissions reduction. The EPA implemented a round of emissions standards, known as Tier 2, for sulfur in gasoline in 2004, reducing sulfur emissions in gas-powered vehicles by 77 to 90 percent. The EPA is scheduled to implement new sulfur regulations -- "Tier 3" -- for gasoline in 2017.
Reid Vapor Pressure
Reid Vapor Pressure is a measure of gasoline volatility, which is regulated by the EPA during summer months -- June 1 to September 15 -- in order to help control heat-related evaporation that can contribute to smog and ozone. Relative amounts of fuel additives can contribute to fuel volatility. Between 1989 and 1991, Phase I of volatility regulation limited RVP to between 9.0 and 10.5 pounds per square inch, depending on the state. After 1992, RVP was limited to 7.8 or 9.0 pounds per square inch. Gasoline that contains 9 or 10 percent ethanol by volume has RVP allowance of 1 pound per square inch.
Oxygenates In Winter
Fuel additives that contain oxygen, usually as alcohol or ether, are oxygenates. They enhance fuel combustion and so can reduce exhaust emissions while improving octane ratings. Oxygenated gasoline is required by the Clean Air Act in locations with particularly poor air quality, where carbon monoxide levels are greater than federal air quality standards allow, especially in the winter months when oxygenated gasoline helps minimize ozone formation and smog. These programs are implemented by the states, so regulations may vary by state.
E15
Ethanol is a renewable fuel currently under research and development that is manufactured using plant biomass. The EPA has now allowed -- but not required -- gasoline on U.S. markets that contain more than ten percent ethanol by volume. Light-duty cars and trucks introduced after 2001 can use fuels up to 15 percent ethanol by volume, as long as the manufacturers meet conditions outlined in two specific partial waivers.
Related Programs
The EPA also has programs in place to regulate emissions, thus protecting air quality and reducing smog. What a vehicle emits is directly related to what fuel it burns, and what additives are in that fuel. Mobile Source Air Toxics rules are designed to protect air quality and limit harmful emissions from vehicles. Reformulated gasoline. or RFG, is another initiative implemented by the EPA in high-smog areas, requiring high-quality gas designed specifically for lower emissions where air quality is poorest. About 30 percent of gasoline sold in the U.S. is RFG.