There are two quality standards for diesel fuels in Japan: a mandatory standard specified in the “Law on the Quality Control of Gasoline and Other Fuels” (“Quality Assurance Law”) and a voluntary Japanese Industrial Standard (JIS) K 2204 “Diesel Fuel”.

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The Quality Assurance Law provides mandatory requirements for sulfur, cetane index and T90 distillation temperature that diesel fuel must meet. It also includes for reference purposes, a standard diesel fuel specification for viscosity and low temperature operability requirements.

In order to accommodate biodiesel fuel blends, the Quality Assurance Law has been amended as outlined in the discussion on Japanese biodiesel standards. The amendments, effective March 2007, include limits on the amount of FAME and triglycerides in diesel fuel to distinguish it from a biodiesel/diesel fuel blend and to prevent the use of unprocessed vegetable oils.

JIS K 2204 specifies five grades of diesel fuel. The main difference between each grade is the low temperature operability limits. The grades are: Special No. 1, No. 1, No. 2, No. 3, and Special No. 3 (1S, 1, 2, 3 and 3S). In order to provide fuel producers some flexibility to produce the different grades, the flash point, T90 distillation temperature, viscosity and cetane index will differ as well.

Since the 1990’s, the sulfur content in diesel fuels in Japan has been reduced in several steps, as follows:

  • 0.2% = 2,000 ppm sulfur limit became effective from 1994
  • 0.05% = 500 ppm S limit from 1997
  • 50 ppm S limit is mandatory from 2005; in practice, 50 ppm S diesel was introduced nationwide from April 2003 through a voluntary effort of the Japanese petroleum industry
  • 10 ppm S limit is effective from 2007; Japanese petroleum industry made a voluntary commitment to supply 10 ppm S fuel from January 2005 (nationwide, with the exception of certain island areas and Okinawa)

Highway vehicles (passenger cars, trucks and buses) normally use No. 2 diesel fuel. Special No. 3 diesel is used as the winter grade in Hokkaido and other cold climate areas. Most Japanese off-road equipment also uses No. 2 diesel fuel grade, with some using fuel oil equivalent to No. 1 of Category I specified by JIS K 2205 (sulfur limit in the latter fuel remains at 0.5%).