1.1 The calculated Cetane Index by Four Variable Equation provides a means for estimating the ASTM cetane number of distillate fuels from density and recovery temperature measurements. The value computed from the equation is termed the Calculated Cetane Index by Four Variable Equation.

1.2 The Calculated Cetane Index by Four Variable Equation is not an optional method for expressing ASTM cetane number. It is a supplementary tool for estimating cetane number when used with due regard for its limitations.

1.3 The test method "Calculated Cetane Index by Four Variable Equation" is particularly applicable to Grade 1-D and Grade 2-D diesel fuel oils containing straight-run and cracked stocks, and blends of the two. It can also be used for heavier fuels with 90% recovery points less than 382°C and for fuels containing non-petroleum derivatives from tar sands and oil shale.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.