Letter Ballot D02.E (03-04)
Contact Person: Donna Hoel
Revision of D976-91 (Reapproved 2000) Standard Test methods for Calculated Index of Distillate Fuels to include a statement regarding application to low sulfur diesel fuels in the Scope.
In recent years many OEM members of Subcommittee E have expressed dissatisfaction with the use of D976, Test Method for Calculated Cetane Index, for the estimation of cetane number of current S500 (low sulfur) on-road diesel fuels. Their preference is the use of Procedure B of D4737, Standard Test Method for Calculated Cetane Index by Four Variable Equation, which was derived using a dataset of S500 diesel fuels from North America.
Subcommittee E has completed balloting language in D975, Specification for Diesel Fuels, that makes clear that D976 is not to be used as an estimate of cetane number, but these members have requested that D976 be changed to put a caution regarding its use for S500 fuels into the test method. The language below is meant to convey this caution.
Current Text Proposed Text
1.2 The Calculated Cetane Index is not an optional method for expressing ASTM cetane number. It is a supplementary tool for predicting cetane number when used with due regard to its limitation. 1.2 The Calculated Cetane Index is not an optional method for expressing ASTM cetane number. It is a supplementary tool for predicting cetane number when used with due regard to its limitation.1.2.1 The Calculated Cetane Index was derived for diesel fuels existing in the 1960's, most of which had sulfur contents over 500 ppm2. It is expected that the Calculated Cetane Index will be most appropriately applied to fuels similar to those used in its derivation, that is, to fuels with sulfur contents over 500 ppm. Diesel fuels with sulfur contents less than 500 ppm would be more appropriately estimated using ASTM Test Method D4737.