Can refiners reduce the number of significant figures required for emissions values from 4 to 3 (the fourth significant figure is not meaningful in these calculations)?
No. Section 80.90(g) states that emission values shall be determined to four (4) significant figures. (7/1/94)
This question and answer was posted at List of Reformulated Gasoline and Anti-Dumping Questions and Answers: July 1, 1994 through November 10, 1997 (pdf)