Understanding the effects of gasoline sulfur level on the in-use fleet is important for assessing emissions inventories and impacts of future policy decisions. This study recruited 93 Tier 2 cars and light trucks from owners in southeast Michigan, covering high-sales vehicles of model years 2007-9 with approximately 20,000-40,000 odometer miles.

Test fuels were two non-ethanol gasolines with properties typical of certification fuel, one at a sulfur content of 5 ppm and the other at 28 ppm (representative of retail fuel in the recruiting area). Emissions for gaseous and particulate matter were measured over the Federal Test Procedure.

• The Effects of Ultra-Low Sulfur Gasoline on Emissions from Tier 2 Vehicles in the In-Use Fleet: Final Study Report (PDF)(66 pp, 3 MB, EPA-420-R-14-002, March 2014, About PDF): includes description of program design, data collection, and statistical analyses
• Appendices for Final Study Report (ZIP)(1 pg, 5 MB, March 2014)
• Final Report Database (XLS)(1 pg, 673 K, March 2014) : contains vehicle, fuel, and emissions data used to perform the analyses
• Documents describing the independent peer review of the draft study report