ASTM D4737-21

Standard Test Method for Calculated Cetane Index by Four Variable Equation

SIGNIFICANCE AND USE
5.1 The Calculated Cetane Index by Four Variable Equation is useful for estimating ASTM cetane number when a test engine is not available for determining this property directly and when cetane improver is not used. It may be conveniently employed for estimating cetane number when the quantity of sample available is too small for an engine rating. In cases where the ASTM cetane number of a fuel has been previously established, the Calculated Cetane Index by Four Variable Equation is useful as a cetane number check on subsequent batches of that fuel, provided the fuel's source and mode of manufacture remain unchanged.  
Note 2: Test Methods D6890 and D7170 may be used to obtain a Derived Cetane Number (DCN) when the quantity of sample is too small for an engine test. These methods do measure the effect of cetane improver.  
5.2 Within the range from 32.5 to 56.5 cetane number, the expected error of prediction of Procedure A of the Calculated Cetane Index by Four Variable Equation will be less than ±2 cetane numbers for 65 % of the distillate fuels evaluated. Errors may be greater for fuels whose properties fall outside the recommended range of application.
SCOPE
1.1 The calculated Cetane Index by Four Variable Equation provides a means for estimating the ASTM cetane number (Test Method D613) of distillate fuels from density and distillation 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 a result by Test Method D613 is not available and if cetane improver is not used. As a supplementary tool, the Calculated Cetane Index by Four Variable equation must be used with due regard for its limitations.  
1.3 Procedure A is to be used for Specification D975, Grades No. 1–D S15, No. 1–D S500, No. 1–D S5000, No. 2–D S15, No. 2–D S5000, and No. 4–D. This method for estimating cetane number was developed by Chevron Research Co.2 Procedure A is based on a data set including a relatively small number of No. 1–D fuels. Test Method D4737 Procedure A may be less applicable to No. 1–D S15, No. 1–D S500, and No. 1–D S5000 than to No. 2–D grade S5000 or to No. 4–D fuels.  
1.3.1 Procedure A has been verified as applicable to Grade No. 2–D S15 diesel fuels.3  
1.4 Procedure B is to be used for Specification D975, Grade No. 2–D S500.  
1.5 The test method “Calculated Cetane Index by Four Variable Equation” is particularly applicable to Grade 1–D S5000, Grade No. 1–D S500, Grade No. 2–D S5000 and Grade No. 2–D S500 diesel fuel oils containing straight-run and cracked stocks, and their blends. It can also be used for heavier fuels with 90 % recovery points less than 382 °C and for fuels containing derivatives from oil sands and oil shale.
Note 1: Sxx is the designation for maximum sulfur level specified for the grade. For example, S500 grades are those with a maximum sulfur limit of 500 ppm (μg/g).  
1.6 Biodiesel blends are excluded from this test method, because they were not part of the datasets use to develop either Procedure A or B.  
1.7 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.8 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.9 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Te...

General Information

• Status: Published
• Publication Date: 31-Oct-2021
• ICS: 75.160.20 - Liquid fuels
• Technical Committee: D02 - Petroleum Products, Liquid Fuels, and Lubricants
• Drafting Committee: D02.E0 - Burner, Diesel and Non-Aviation Gas Turbine Fuels

Relations

• Refers: ASTM D613-24 - Standard Test Method for Cetane Number of Diesel Fuel Oil
• Effective Date: 01-Feb-2024
• Refers: ASTM D4175-23a - Standard Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
• Effective Date: 15-Dec-2023
• Refers: ASTM D975-23a - Standard Specification for Diesel Fuel
• Effective Date: 15-Dec-2023
• Refers: ASTM D86-23a - Standard Test Method for Distillation of Petroleum Products and Liquid Fuels at Atmospheric Pressure
• Effective Date: 01-Dec-2023
• Refers: ASTM D86-23ae1 - Standard Test Method for Distillation of Petroleum Products and Liquid Fuels at Atmospheric Pressure
• Effective Date: 01-Dec-2023
• Refers: ASTM D4175-23e1 - Standard Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
• Effective Date: 01-Jul-2023
• Refers: ASTM D2887-23 - Standard Test Method for Boiling Range Distribution of Petroleum Fractions by Gas Chromatography
• Effective Date: 01-Jul-2023
• Refers: ASTM D2887-19 - Standard Test Method for Boiling Range Distribution of Petroleum Fractions by Gas Chromatography
• Effective Date: 01-Jul-2019
• Refers: ASTM D975-19 - Standard Specification for Diesel Fuel Oils
• Effective Date: 01-Feb-2019
• Refers: ASTM D975-18a - Standard Specification for Diesel Fuel Oils
• Effective Date: 01-Dec-2018
• Refers: ASTM D6751-18 - Standard Specification for Biodiesel Fuel Blend Stock (B100) for Middle Distillate Fuels
• Effective Date: 01-Oct-2018
• Refers: ASTM D975-17a - Standard Specification for Diesel Fuel Oils
• Effective Date: 15-Dec-2017
• Refers: ASTM D613-17c - Standard Test Method for Cetane Number of Diesel Fuel Oil
• Effective Date: 01-Dec-2017
• Refers: ASTM D975-17 - Standard Specification for Diesel Fuel Oils
• Effective Date: 01-May-2017
• Refers: ASTM D613-17a - Standard Test Method for Cetane Number of Diesel Fuel Oil
• Effective Date: 01-May-2017

Overview

ASTM D4737-21: Standard Test Method for Calculated Cetane Index by Four Variable Equation is a key test method developed by ASTM International. It provides a means for estimating the cetane number of distillate fuels-crucial for characterizing diesel ignition quality-using a mathematical relationship based on the fuel's density and distillation recovery temperatures. This calculated cetane index serves as a practical alternative when direct engine testing per ASTM D613 is not feasible and no cetane improver is used.

This method is especially valuable when only small fuel samples are available or for verifying the consistency of production batches, provided the fuel’s composition and manufacturing process remain unchanged.

Key Topics

• Cetane Index Estimation: Utilizes a four variable equation leveraging density at 15°C and 10%, 50%, and 90% distillation recovery temperatures.
• Applicability: Designed primarily for distillate diesel fuels under ASTM D975, including Grades No. 1–D S15, No. 1–D S500, No. 1–D S5000, No. 2–D S15, No. 2–D S500, No. 2–D S5000, and No. 4–D.
• Two Procedures:
  • Procedure A: For most diesel fuel grades covered under D975, including No. 1–D, No. 2–D, and No. 4–D.
  • Procedure B: Specifically for Grade No. 2–D S500.
• Scope Limitations:
  • Not applicable to fuels containing cetane improvers, biodiesel blends, or pure hydrocarbons/non-petroleum fuels.
  • Precision is tied directly to the quality of the density and distillation data.

Applications

ASTM D4737-21’s calculated cetane index is used for:

• Quality Control: Quickly estimating cetane number in fuel quality assessments when engine-based testing is impractical.
• Batch Verification: Confirming cetane number consistency in sequential production batches of distillate diesel fuels.
• Small Sample Evaluation: Providing reliable cetane estimations when available sample volume is insufficient for engine tests.
• Process Oversight: Supporting refineries and fuel suppliers with a rapid alternative for cetane number validation throughout the supply chain.
• Regulatory and Specification Compliance: Facilitating evaluation of fuels to meet standards such as ASTM D975, important for regulatory approval and marketplace acceptance.

Note: The method is not valid for fuels with cetane improver additives or biodiesel blends, according to ASTM D6751 and EN 14214.

Related Standards

ASTM D4737-21 references or complements several related standards:

• ASTM D613: Standard Test Method for Cetane Number of Diesel Fuel Oil (primary engine test method).
• ASTM D86: Distillation of Petroleum Products and Liquid Fuels at Atmospheric Pressure (for distillation recovery temperatures).
• ASTM D975: Specification for Diesel Fuel Oils (defining grades used in this method).
• ASTM D1298 / D4052: Methods for measuring density or API gravity of liquids.
• ASTM D2887: Boiling Range Distribution by Gas Chromatography (alternative for distillation data, with specific conversion).
• ASTM D6890: Ignition Delay and Derived Cetane Number by Constant Volume Chamber (for DCN as an alternative when engine testing is impractical).
• EN 14214: European specification for biodiesel, explicitly excluded from this test method.

Practical Value

Adoption of ASTM D4737-21 delivers significant value for petroleum laboratories, refineries, regulatory agencies, and suppliers through:

• Efficient quality assurance for diesel distillates.
• Cost-effective testing without the need for complex engine test setups.
• Rapid and reliable cetane estimation to inform procurement, processing, and regulatory compliance.

In summary, ASTM D4737-21 is a crucial standard for routine diesel fuel quality management, enabling stakeholders to estimate cetane index efficiently and maintain high standards in the global fuel supply chain.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D4737 − 21
Standard Test Method for
Calculated Cetane Index by Four Variable Equation
This standard is issued under the fixed designation D4737; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope* cracked stocks, and their blends. It can also be used for heavier
fuels with 90 % recovery points less than 382 °C and for fuels
1.1 The calculated Cetane Index by Four Variable Equation
containing derivatives from oil sands and oil shale.
provides a means for estimating the ASTM cetane number
(Test Method D613) of distillate fuels from density and
NOTE 1—Sxx is the designation for maximum sulfur level specified for
the grade. For example, S500 grades are those with a maximum sulfur
distillation recovery temperature measurements. The value
limit of 500 ppm (µg/g).
computed from the equation is termed the Calculated Cetane
Index by Four Variable Equation. 1.6 Biodiesel blends are excluded from this test method,
because they were not part of the datasets use to develop either
1.2 The Calculated Cetane Index by Four Variable Equation
Procedure A or B.
isnotanoptionalmethodforexpressingASTMcetanenumber.
It is a supplementary tool for estimating cetane number when 1.7 The values stated in SI units are to be regarded as
a result by Test Method D613 is not available and if cetane standard. No other units of measurement are included in this
improver is not used. As a supplementary tool, the Calculated standard.
Cetane Index by Four Variable equation must be used with due
1.8 This standard does not purport to address all of the
regard for its limitations.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
1.3 Procedure A is to be used for Specification D975,
priate safety, health, and environmental practices and deter-
Grades No. 1–D S15, No. 1–D S500, No. 1–D S5000, No. 2–D
mine the applicability of regulatory limitations prior to use.
S15, No. 2–D S5000, and No. 4–D.This method for estimating
1.9 This international standard was developed in accor-
cetane number was developed by Chevron Research Co.
dance with internationally recognized principles on standard-
Procedure A is based on a data set including a relatively small
ization established in the Decision on Principles for the
number of No. 1–D fuels. Test Method D4737 Procedure A
Development of International Standards, Guides and Recom-
maybelessapplicabletoNo. 1–DS15,No.1–DS500,andNo.
mendations issued by the World Trade Organization Technical
1–D S5000 than to No. 2–D grade S5000 or to No. 4–D fuels.
Barriers to Trade (TBT) Committee.
1.3.1 Procedure A has been verified as applicable to Grade
No. 2–D S15 diesel fuels.
2. Referenced Documents
1.4 Procedure B is to be used for Specification D975, Grade
2.1 ASTM Standards:
No. 2–D S500.
D86 Test Method for Distillation of Petroleum Products and
1.5 The test method “Calculated Cetane Index by Four
Liquid Fuels at Atmospheric Pressure
Variable Equation” is particularly applicable to Grade 1–D
D613 Test Method for Cetane Number of Diesel Fuel Oil
S5000, Grade No. 1–D S500, Grade No. 2–D S5000 and Grade
D975 Specification for Diesel Fuel
No. 2–D S500 diesel fuel oils containing straight-run and
D1298 Test Method for Density, Relative Density, or API
Gravity of Crude Petroleum and Liquid Petroleum Prod-
ucts by Hydrometer Method
This test method is under the jurisdiction of ASTM Committee D02 on
D2887 Test Method for Boiling Range Distribution of Pe-
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
troleum Fractions by Gas Chromatography
Subcommittee D02.E0 on Burner, Diesel and Non-Aviation Gas Turbine Fuels.
D4052 Test Method for Density, Relative Density, and API
Current edition approved Nov. 1, 2021. Published November 2021. Originally
approved in 1987. Last previous edition approved in 2016 as D4737 – 10 (2016).
Gravity of Liquids by Digital Density Meter
DOI: 10.1520/D4737-21.
D4175 Terminology Relating to Petroleum Products, Liquid
Ingham, M. C., et al., “Improved Predictive Equations for Cetane Number,”
SAE Paper No 860250, Society of Automotive Engineers (SAE), 400 Common-
wealth Dr., Warrendale, PA 15096-0001.
3 4
Supporting data (the analysis leading to the use of ProcedureAfor No. 2-D S15 For referenced ASTM standards, visit the ASTM website, www.astm.org, or
diesel fuels and to Procedure B) have been filed at ASTM International Headquar- contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
ters and may be obtained by requesting Research Report RR:D02-1699. Contact Standards volume information, refer to the standard’s Document Summary page on
ASTM Customer Service at [e-mail]. the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4737 − 21
Fuels, and Lubricants accounted for measurement errors in the independent variables
D6751 Specification for Biodiesel Fuel Blend Stock (B100) (fuel properties) as well as in the dependent variable (cetane
for Middle Distillate Fuels number by Test Method D613). The data base consisted of
D6890 Test Method for Determination of Ignition Delay and 1229 fuels including; commercial diesel fuels, refinery blend-
Derived Cetane Number (DCN) of Diesel Fuel Oils by ing components and fuels derived from oil sands, shale, and
Combustion in a Constant Volume Chamber coal. The analysis also accounted for bias amongst the indi-
D7170 Test Method for Determination of Derived Cetane vidual sets of data comprising the database.
Number (DCN) of Diesel Fuel Oils—Fixed Range Injec-
4.3 ProcedureBhasbeendevelopedfordieselfuelsmeeting
tion Period, Constant Volume Combustion Chamber
the requirements of Specification D975 Grade No. 2–D S500.
Method (Withdrawn 2019)
The relationship is given by the following equation:
2.2 CEN Standards:
CCI52399.90~D!10.1113 ~T !10.1212 ~T !10.0627 ~T !
10 50 90
EN 14214 Automotive fuels — Fatty acid methyl esters
1309.33 (2)
(FAME) for diesel engines — Requirements and test
methods
where:
CCI = Calculated Cetane Index by Four Variable Equation,
3. Terminology
D = Density at 15 °C, g/mL determined by Test Methods
3.1 For definitions of terms used in this test method, refer to
D1298 or D4052,
Terminology D4175.
T = 10 % recovery temperature, °C, determined by Test
Method D86 and corrected to standard barometric
4. Summary of Test Method
pressure,
T = 50 % recovery temperature, °C, determined by Test
4.1 Two correlations in SI units have been established 50
Method D86 and corrected to standard barometric
between the ASTM cetane number and the density and 10 %,
pressure, and
50 %, and 90 % distillation recovery temperatures of the fuel.
T = 90 % recovery temperature, °C, determined by Test
Procedure A has been developed for diesel fuels meeting the 90
Method D86 and corrected to standard barometric
requirements of Specification D975 Grades No. 1–D S15, No.
pressure.
1–D S500, No. 1–D S5000, No. 2–D S5000, and No. 4–D. It
has been found to be applicable to Grade No. 2–D S15. The
4.3.1 The equation for Procedure B when T ,T , and T
10 50 90
relationship is given by the following equation:
are in °F is:
CCI 5 45.21 0.0892 T 1 0.1311 0.901 B T 1 0.0523
~ !~ ! @ ~ !~ !#@ # @
CCI52399.90~D!10.06183 ~T !10.06733 ~T !10.03483 ~T !
10N 50N
10 50 90
2 2
2 0.420 B T 1 0.00049 T 2 T 1 107 B
~ !~ !#@ # @ #@~ ! ~ ! # ~ !~ ! 1304.09 (3)
90N 10N 90N
1~60!~B! (1)
where:
where:
CCI = Calculated Cetane Index by Four Variable Equation,
D = Density at 15 °C, g/mL determined by Test Method
CCI = Calculated Cetane Index by Four Variable Equation,
D1298 or D4052,
D = Density at 15 °C, g/mL determined by Test Methods
T = 10 % recovery temperature, °F, determined by Test
D1298 or D4052, 10
Method D86 and corrected to standard barometric
DN = D - 0.85,
(-3.5)(DN)
B =[e ]-1, pressure,
T = 50 % recovery temperature, °F, determined by Test
T = 10 % recovery temperature, °C, determined by Test
10 50
Method D86 and corrected to standard barometric Method D86 and corrected to standard barometric
pressure, and
pressure,
T =T - 215, T = 90 % recovery temperature, °F, determined by Test
10N 10
T = 50 % recovery temperature, °C, determined by Test
Method D86 and corrected to standard barometric
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D4737 − 10 (Reapproved 2016) D4737 − 21
Standard Test Method for
Calculated Cetane Index by Four Variable Equation
This standard is issued under the fixed designation D4737; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope Scope*
1.1 The calculated Cetane Index by Four Variable Equation provides a means for estimating the ASTM cetane number (Test
Method D613) of distillate fuels from density and distillation 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 a result by Test Method D613 is not available and if cetane improver is
not used. As a supplementary tool, the Calculated Cetane Index by Four Variable equation must be used with due regard for its
limitations.
1.3 Procedure A is to be used for Specification D975, Grades No. 1–D S15, No. 1–D S500, No. 1–D S5000, No. 2–D S15, No.
2–D S5000, and No. 4–D. This method for estimating cetane number was developed by Chevron Research Co. Procedure A is
based on a data set including a relatively small number of No. 1–D fuels. Test Method D4737 Procedure A may be less applicable
to No. 1–D S15, No. 1–D S500, and No. 1–D S5000 than to No. 2–D grade S5000 or to No. 4–D fuels.
1.3.1 Procedure A has been verified as applicable to Grade No. 2–D S15 diesel fuels.
1.4 Procedure B is to be used for Specification D975, Grade No. 2–D S500.
1.5 The test method “Calculated Cetane Index by Four Variable Equation” is particularly applicable to Grade 1–D S5000, Grade
No. 1–D S500, Grade No. 2–D S5000 and Grade No. 2–D S500 diesel fuel oils containing straight-run and cracked stocks, and
their blends. It can also be used for heavier fuels with 90 % recovery points less than 382 °C and for fuels containing derivatives
from oil sands and oil shale.
NOTE 1—Sxx is the designation for maximum sulfur level specified for the grade. For example, S500 grades are those with a maximum sulfur limit of
500 ppm (μg/g).
1.6 Biodiesel blends are excluded from this test method, because they were not part of the datasets use to develop either Procedure
A or B.
This test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcommittee
D02.E0 on Burner, Diesel, Diesel and Non-Aviation Gas Turbine, and Marine Turbine Fuels.
Current edition approved July 1, 2016Nov. 1, 2021. Published July 2016November 2021. Originally approved in 1987. Last previous edition approved in 20102016 as
D4737 – 10. 10 (2016). DOI: 10.1520/D4737-10R16.10.1520/D4737-21.
Ingham, M. C., et al., “Improved Predictive Equations for Cetane Number,” SAE Paper No 860250, Society of Automotive Engineers (SAE), 400 Commonwealth Dr.,
Warrendale, PA 15096-0001.
Supporting data (the analysis leading to the use of Procedure A for No. 2-D S15 diesel fuels and to Procedure B) have been filed at ASTM International Headquarters
and may be obtained by requesting Research Report RR:D02-1699. Contact ASTM Customer Service at [e-mail].
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4737 − 21
1.7 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.8 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.9 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D86 Test Method for Distillation of Petroleum Products and Liquid Fuels at Atmospheric Pressure
D613 Test Method for Cetane Number of Diesel Fuel Oil
D975 Specification for Diesel Fuel
D1298 Test Method for Density, Relative Density, or API Gravity of Crude Petroleum and Liquid Petroleum Products by
Hydrometer Method
D2887 Test Method for Boiling Range Distribution of Petroleum Fractions by Gas Chromatography
D4052 Test Method for Density, Relative Density, and API Gravity of Liquids by Digital Density Meter
D4175 Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
D6751 Specification for Biodiesel Fuel Blend Stock (B100) for Middle Distillate Fuels
D6890 Test Method for Determination of Ignition Delay and Derived Cetane Number (DCN) of Diesel Fuel Oils by Combustion
in a Constant Volume Chamber
D7170 Test Method for Determination of Derived Cetane Number (DCN) of Diesel Fuel Oils—Fixed Range Injection Period,
Constant Volume Combustion Chamber Method (Withdrawn 2019)
2.2 CEN Standards:
EN 14214 Automotive fuels — Fatty acid methyl esters (FAME) for diesel engines — Requirements and test methods
3. Terminology
3.1 For definitions of terms used in this test method, refer to Terminology D4175.
4. Summary of Test Method
4.1 Two correlations in SI units have been established between the ASTM cetane number and the density and 10 %, 50 %, and
90 % distillation recovery temperatures of the fuel. Procedure A has been developed for diesel fuels meeting the requirements of
Specification D975 Grades No. 1–D S15, No. 1–D S500, No. 1–D S5000, No. 2–D S5000, and No. 4–D. It has been found to be
applicable to Grade No. 2–D S15. The relationship is given by the following equation:
2 2 2
CCI 5 45.21 0.0892 T 1@0.1311 0.901 B #@T #1@0.0523 2 0.420 B #@T #1@0.00049#@ T 2 T #1 107 B 1 60 B (1)
~ ! ~ ! ~ !~ ! ~ !~ ! ~ ! ~ ! ~ !~ ! ~ !~ !
10N 50N 90N 10N 90N
where:
CCI = Calculated Cetane Index by Four Variable Equation,
D = Density at 15 °C, g/mL determined by Test Methods D1298 or D4052,
DN = D - 0.85,
(-3.5)(DN)
B = [e ] - 1,
T = 10 % recovery temperature, °C, determined by Test Method D86 and corrected to standard barometric pressure,
T = T - 215,
10N 10
T = 50 % recovery temperature, °C, determined by Test Method D86 and corrected to standard barometric pressure,
T = T - 260,
50N 50
T = 90 % recovery temperature, °C, determined by Test Method D86 and corrected to standard barometric pressure, and
T = T - 310.
90N 90
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
The last approved version of this historical standard is referenced on www.astm.org.
Available from the National CEN members listed on the CEN website (www.cenorm.be) or from the CEN/TC 19 Secretariat ([e-mail]).
D4737 − 21
4.2 The empirical equation for Procedure A of the Calculated Cetane Index by Four Variable Equation was derived using a
generalized least squares fitting technique which accounted for measurement errors in the independent variables (fuel properties)
as well as in the dependent variable (cetane number by Test Method D613). The data base consisted of 1229 fuels including;
commercial diesel fuels, refinery blending components and fuels derived from oil sands, shale, and coal. The analysis also
accounted for bias amongst the individual sets of data comprising the database.
4.3 Procedure B has been developed for diesel fuels meeting the requirements of Specification D975 Grade No. 2–D S500. The
relationship is given by the following equation:
CCI 52399.90 D 10.1113 T 10.1212 T 10.0627 T 1309.33 (2)
~ ! ~ ! ~ ! ~ !
10 50 90
where:
CCI = Calculated Cetane Index by Four Variable Equation
D = Density at 15 °C, g/mL determined by Test Methods D1298 or D4052
T = 10 % recovery temperature, °C, determined by Test Method D86 and corrected to standard barometric pressure
T = 50 % recovery temperature, °C, determined by Test Method D86 and corrected to standard barometric pressure
T = 90 % recovery temperature, °C, determined by Test Method D86 and corrected to standard barometric pressure
CCI = Calculated Cetane Index by Four Variable Equation,
D = Density at 15 °C, g/mL determined by Test Methods D1298 or D4052,
T = 10 % recovery temperature, °C, determined by Test Method D86 and corrected to standard barometric pressure,
T = 50 % recovery temperature, °C, determined by Test Method D86 and corrected to standard barometric pressure, and
T = 90 % recovery temperature, °C, determined by Test
...