These test programs and modeling estimate the emissions impacts of changes in fuel properties and composition. 

• Biodiesel Emissions Analysis Program: uses existing data to quantify the air pollution emission effects of biodiesel for diesel engines that have not been specifically modified to operate on biodiesel. The program examines the emission impacts of biodiesel and biodiesel/diesel blends for both regulated and unregulated pollutants, as well as fuel economy.
• Computer Models Related to the Reformulated Gasoline (RFG) Program: Complex model used to analyze RFG and anti-dumping emissions performance standards.
• EPAct/V2/E-89 Tier 2 Gasoline Fuel Effects Study: a program jointly sponsored by EPA, DOE/NREL, and the Coordinating Research Council examining the effects of five parameters (aromatics, ethanol, RVP, T50, T90) on exhaust emissions from light-duty Tier 2 vehicles.
• Heavy-Duty Diesel Fuel Analysis: sought to quantify the air pollution emission effects of diesel fuel parameters on various nonroad and highway heavy-duty diesel engines. The program examined the hydrocarbon (HC), oxides of nitrogen (NOx) and particulate matter (PM) emission impacts of diesel fuel parameters including such parameters as cetane number, aromatics content, and fuel density.
• Ultra-Low Sulfur Gasoline Emissions Study: EPA's study of effects of low sulfur gasoline (< 10ppm) on Tier 2 vehicles recruited from the in-use fleet.
• Tier 3 Certification Fuel Impacts Test Program: EPA’s study comparing CO2 emissions and fuel economy performance of Tier 2 and Tier 3 certification test gasolines.  This study provides data to inform fuel economy and GHG test procedure adjustments needed to accommodate changes to certification fuel included in the Tier 3 regulatory program.