regulation of fuels and fuel additives modifications to renewable fuel standard and diesel sulfur programs 14 pages english epa is proposing to amend the definition of heating oil in the renewable fuel standard rfs program under section 211 o of the clean air act. this amendment would expand the scope of renewable fuels that can generate renewable identification numbers rins as heating oil to include fuel oil produced from qualifying renewable biomass that would be used to generate heat to warm buildings or other facilities where people live work recreate or conduct other activities. fuel oils used to generate process heat power or other functions would not be included in the amended definition. producers or importers of fuel oil that meets the amended definition of heating oil would be allowed to generate rins provided that the fuel oil meets the other requirements specified in the rfs regulations. this proposed amendment would not modify or limit fuel included in the current definition of heating oil. we are also proposing amendments to the diesel sulfur program to provide additional flexibility for transmix processors that produce locomotive and marine diesel fuel. specifically we are proposing to reinstate an allowance for transmix processors to produce 500 parts per million ppm sulfur diesel fuel for use in older technology locomotive and marine diesel outside of the northeast mid-atlantic area. we are also requesting comment on extending this allowance to outside of the northeast mid-atlantic area. these proposed amendments to the diesel transmix provisions are expected to result in reduced compliance costs for transmix processors and users of locomotive and marine diesel fuel while having a neutral or positive environmental impact. epa is also proposing to amend the fuel marker requirements for 500 ppm sulfur locomotive and marine lm diesel fuel to address an oversight in the original rulemaking where the regulations failed to incorporate provisions described in the rulemaking preamble to allow for solvent yellow 124 marker to transition out of the distribution system.