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Fuels and Fuel Additives

Gasoline Sulfur Program

Gasoline Sulfur

Sulfur is a natural component in crude oil that ends up in gasoline and diesel unless removed. Sulfur in gasoline impairs the effectiveness of emission control systems and contributes to air pollution. Reducing the sulfur content in gasoline enables advanced emission controls and reduces air pollution.

The Tier 3 program is a comprehensive approach, considering the vehicle and its fuel as an integrated system, aimed at addressing the impacts of motor vehicles on air quality and public health. The program sets new vehicle emissions standards and lowers the sulfur content of gasoline beginning in 2017. The vehicle standards will reduce both tailpipe and evaporative emissions from passenger cars, light-duty trucks, medium-duty passenger vehicles, and some heavy-duty vehicles. The gasoline sulfur standard will enable more stringent vehicle emissions standards and will make emissions control systems more effective.

The Tier 2 Gasoline Sulfur program reduced the sulfur content of gasoline by up to 90 percent, enabling the use of new emission control technologies in cars and trucks that reduce harmful air pollution. The Tier 2 program marked the first time EPA treated vehicles and fuels as a system. The program grew out of a Clean Air Act requirement that EPA consider the need, feasibility, and cost-effectiveness of stronger tailpipe emission standards beginning in 2004. Requirements for use of low-sulfur gasoline enabled use of advanced emission control systems in cars, pickups, SUVs, and vans beginning in model year 2004. Vehicles meeting Tier 2 emission standards are 77 to 95 percent cleaner than earlier models.

Regulatory Programs:


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Please visit EPA's Transportation and Air Quality web-based repository of mobile source documents, Document Index System (DIS). This searchable repository contains regulations, Federal Register notices, policy letters, and guidance documents.

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