40 CFR §1065.703

1. (a)Distillate diesel fuels for testing must be clean and bright, with pour and cloud points adequate for proper engine operation.
2. (b)There are three grades of #2 diesel fuel specified for use as a test fuel. See the standard-setting part to determine which grade to use. If the standard-setting part does not specify which grade to use, use good engineering judgment to select the grade that represents the fuel on which the engines will operate in use. The three grades are specified in Table 1 of this section.
3. (c)You may use the following nonmetallic additives with distillate diesel fuels:
   1. (1)Cetane improver.
   2. (2)Metal deactivator.
   3. (3)Antioxidant, dehazer.
   4. (4)Rust inhibitor.
   5. (5)Pour depressant.
   6. (6)Dye.
   7. (7)Dispersant.
   8. (8)Biocide.