Study of refining capability requirements, corresponding capital investment requirements, and per-liter refining costs to transition to ultra-low sulfur gasoline and diesel fuel in India, Mexico, Brazil and China. Advanced emission control technologies in engines and vehicles require clean fuels, especially ultra-low sulfur gasoline (ULSG) and diesel fuel (ULSD). In the past decade, many countries with developed economies, including the United States, Canada, Western Europe and Japan, have made a transition to ultra-low sulfur fuels (ULSF), in particular ULSG and ULSD. For example, in 2006, the U.S. implemented gasoline and diesel sulfur standards of 30 ppm (average) and 10 ppm (cap), respectively. These countries also have adopted tighter standards on gasoline volatility, aromatics content and benzene content, and on diesel fuel aromatics content and cetane number.