The International Fuel Quality Center has ranked the top 100 countries based on sulfur limits in on-road diesel and found that 44 countries can now boast that their on-road diesel fuel is the cleanest in the world.

"Sulfur reduction remains essential and unique, as it is the only component of the refining process for petroleum fuels that lowers all airborne pollutants from the transport sector," according to Liisa Kiuru-Griffith, executive director, IFQC. "This is why there is added pressure and a movement to reduce sulfur limits in other categories, like marine fuels."

The top 47 countries share a maximum sulfur limit of 15 ppm or less with varying implementation timelines. Sweden, Germany and Japan topped the list. Canada ranked 45th, and the U.S. ranked 46th, both at 15ppm sulfar.

Six countries advanced in the 2012 list, led by Ecuador, which joined the top 100 by lowering its maximum sulfur limit from 7,000 ppm to 500 ppm and moving up 47 spots to number 83. Saudi Arabia joined Ecuador at number 83 by rising 23 spots. Its maximum diesel sulfur content was lowered from 800 ppm to 500 ppm.

"With distillates experiencing the largest growth among all petroleum products globally, it makes it even more challenging to achieve such strict quality requirements," says Kristine Klavers, senior vice president, Hart Energy.

Consumers with 2007 or later model year diesel vehicles should only fuel them with ultra-low sulfur diesel. ULSD is a cleaner-burning diesel fuel that contains 97% less sulfur than low-sulfur diesel. ULSD was developed to allow the use of diesel particulate filters that reduce diesel emissions more effectively but can be damaged by sulfur.

IFQC's analysts based the rankings on maximum allowable limits in national standards and year of implementation. The complete list can be found at