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The U.S. EPA has proposed a Tier 3 rule to lower average NMOG+NOx emissions from new light duty vehicles by approximately 80% from 2017 to 2025. Early in this time period, gasoline-fueled vehicles are expected to use technologies similar to California SULEV-II/PZEV certified models currently in limited production. These late model vehicles feature engine control systems that promote rapid catalyst light-off and are designed for ultra-high catalyst conversion efficiency. To enable the use of advanced catalyst coatings and materials, the EPA is also proposing to limit the sulfur content of gasoline to an annual average of 10 ppm while optionally maintaining the current maximum cap of 80 ppm. Fuel sulfur is known to poison precious metal-based catalysts, and the impact on emissions is well understood for older technology vehicles. However, there is a lack of test data on the sensitivity and reversibility of late model vehicle emissions to sulfur.