ASTM D7593-22

Standard Test Method for Determination of Fuel Dilution for In-Service Engine Oils by Gas Chromatography

SIGNIFICANCE AND USE
5.1 Some fuel dilution of in-service engine oil is normal under typical operating conditions. However, excessive fuel dilution can lead to decreased performance, premature wear, or sudden engine failure. This test method provides a means of quantifying the level of fuel dilution, allowing the user to take necessary action. This test method does not purport to accurately quantify the specific fuel present in the in-service lubricant samples due to limitations associated with the aging and degradation of the fuel in the crankcase. Rather, quantification of diesel fuel is normalized using a simulated aged fuel.
SCOPE
1.1 This test method covers the determination of fuel dilution for in-service engine oil by gas chromatography.  
1.2 Analysis can be performed directly by this test method without pretreatment or dilution of the sample.  
1.3 There is no limitation for the determination of the dilution range, provided the amount of sample is within the linear range of the gas chromatograph detector. However, sample dilution can add potential error to the result and may affect the precision obtained as compared to the values presented in Section 14, which were obtained with no dilution.  
1.4 This test method covers a quantitation range up to 10 % (m/m) for diesel and biodiesel, and up to 5 % (m/m) for gasoline.  
1.5 The values stated in SI units are to be regarded as standard. Where non-SI units are provided, they are shown in parentheses.  
1.6 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.  
1.7 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.

General Information

• Status: Published
• Publication Date: 30-Nov-2022
• ICS: 75.100 - Lubricants, industrial oils and related products
• ICS: 75.160.20 - Liquid fuels
• Technical Committee: D02 - Petroleum Products, Liquid Fuels, and Lubricants
• Drafting Committee: D02.96.02 - Chemistry for the Evaluation of In-Service Lubricants

Relations

• Refers: ASTM D4175-23a - Standard Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
• 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 E594-96(2019) - Standard Practice for Testing Flame Ionization Detectors Used in Gas or Supercritical Fluid Chromatography
• Effective Date: 01-Sep-2019
• Refers: ASTM D86-16 - Standard Test Method for Distillation of Petroleum Products and Liquid Fuels at Atmospheric Pressure
• Effective Date: 01-Jul-2016
• Refers: ASTM D3525-04(2016) - Standard Test Method for Gasoline Diluent in Used Gasoline Engine Oils by Gas Chromatography
• Effective Date: 01-Apr-2016
• Refers: ASTM D86-11b - Standard Test Method for Distillation of Petroleum Products at Atmospheric Pressure
• Effective Date: 01-Dec-2011
• Refers: ASTM E594-96(2011) - Standard Practice for Testing Flame Ionization Detectors Used in Gas or Supercritical Fluid Chromatography
• Effective Date: 01-Nov-2011
• Refers: ASTM D3525-04(2010) - Standard Test Method for Gasoline Diluent in Used Gasoline Engine Oils by Gas Chromatography
• Effective Date: 01-Oct-2010
• Refers: ASTM D86-09 - Standard Test Method for Distillation of Petroleum Products at Atmospheric Pressure
• Effective Date: 15-Apr-2009
• Refers: ASTM D86-08a - Standard Test Method for Distillation of Petroleum Products at Atmospheric Pressure
• Effective Date: 15-Dec-2008
• Refers: ASTM D86-08 - Standard Test Method for Distillation of Petroleum Products at Atmospheric Pressure
• Effective Date: 15-Nov-2008
• Refers: ASTM D86-07b - Standard Test Method for Distillation of Petroleum Products at Atmospheric Pressure
• Effective Date: 15-Nov-2007
• Refers: ASTM D86-07a - Standard Test Method for Distillation of Petroleum Products at Atmospheric Pressure
• Effective Date: 01-Apr-2007

Overview

ASTM D7593-22 specifies a standardized test method for the determination of fuel dilution in in-service engine oils using gas chromatography. Fuel dilution in lubricating oil can occur in engines operating under normal conditions, but elevated levels may lead to decreased performance, excessive wear, and even sudden engine failure. This standard enables laboratories and maintenance professionals to accurately quantify fuel contamination in used engine oil, providing essential data for proactive maintenance and reliability improvements.

This method is applicable to a variety of engine oil types, including those used with diesel, biodiesel, and gasoline fuels. Its robust approach ensures reliable monitoring of fuel dilution, supporting engine diagnostics, oil condition monitoring programs, and maintenance decisions.

Key Topics

• Fuel Dilution Measurement
  The test method determines the percentage of unburned fuel present in in-service lubricant samples. Quantitative analysis covers up to 10% by mass (m/m) for diesel and biodiesel, and up to 5% for gasoline.

• Direct Sample Analysis
  The gas chromatography technique used in ASTM D7593-22 allows analysis of oil samples without any pretreatment or prior dilution, reducing the risk of introducing additional errors and maintaining analytical precision.

• Normalization and Calibration
  The method normalizes diesel measurements with simulated aged fuel standards. While it quantifies fuel dilution, it does not distinguish between different types of fuel blends or account for the impact of aging and degradation in the engine crankcase.

• Instrumentation and Detection
  The procedure requires a gas chromatograph with a split capillary injector, a flame ionization detector (FID), and the capacity for back-flush operations. Marker peaks are used to distinguish fuel components from oil fractions.

• Precision and Reporting
  The standard outlines repeatability data for diesel, biodiesel, and gasoline, enhancing trust in results crucial for informed maintenance actions.

Applications

ASTM D7593-22 serves a vital role in a range of professional and industrial scenarios:

• Engine Condition Monitoring
  Detect excessive fuel dilution in engine oils to identify mechanical issues such as injector leaks or incomplete combustion.

• Predictive Maintenance
  Use fuel dilution data to schedule oil changes or engine repairs before significant wear or failure occurs.

• Quality Assurance
  Ensure lubricants used in fleets, heavy machinery, or critical systems meet operational standards throughout their service life.

• Laboratory Analysis
  Oil testing laboratories can adopt this method for consistent, reliable fuel dilution analysis in routine used oil analysis (UOA) programs.

• Environmental Compliance
  Monitor lubricant condition to optimize oil replacement intervals and minimize unnecessary waste oil disposal.

Related Standards

Several ASTM standards and terminology documents complement or reference ASTM D7593-22, including:

• ASTM D86: Distillation of Petroleum Products and Liquid Fuels at Atmospheric Pressure
• ASTM D3524: Diesel Fuel Diluent in Used Diesel Engine Oils by Gas Chromatography
• ASTM D3525: Gasoline Fuel Dilution in Used Gasoline Engine Oils by Wide-Bore Capillary Gas Chromatography
• ASTM D4175: Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
• ASTM E355/E594/E1510: Practices for gas chromatography terms, flame ionization detector procedures, and column installation

These related documents support enhanced understanding, accurate testing, and broader implementation of oil analysis techniques using gas chromatography.

---

By following ASTM D7593-22, organizations can maintain engine health, optimize lubricant usage, and ensure compliance with both operational and environmental best practices through reliable in-service oil testing for fuel dilution.

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: D7593 − 22
Standard Test Method for
Determination of Fuel Dilution for In-Service Engine Oils by
Gas Chromatography
This standard is issued under the fixed designation D7593; 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* D86 Test Method for Distillation of Petroleum Products and
Liquid Fuels at Atmospheric Pressure
1.1 This test method covers the determination of fuel
D3524 Test Method for Diesel Fuel Diluent in Used Diesel
dilution for in-service engine oil by gas chromatography.
Engine Oils by Gas Chromatography
1.2 Analysis can be performed directly by this test method
D3525 Test Method for Gasoline Fuel Dilution in Used
without pretreatment or dilution of the sample.
Gasoline Engine Oils by Wide-Bore Capillary Gas Chro-
1.3 There is no limitation for the determination of the matography
D4175 Terminology Relating to Petroleum Products, Liquid
dilution range, provided the amount of sample is within the
linear range of the gas chromatograph detector. However, Fuels, and Lubricants
E355 Practice for Gas Chromatography Terms and Relation-
sample dilution can add potential error to the result and may
affect the precision obtained as compared to the values pre- ships
E594 Practice for Testing Flame Ionization Detectors Used
sented in Section 14, which were obtained with no dilution.
in Gas or Supercritical Fluid Chromatography
1.4 This test method covers a quantitation range up to 10 %
E1510 Practice for Installing Fused Silica Open Tubular
(m/m) for diesel and biodiesel, and up to 5 % (m/m) for
Capillary Columns in Gas Chromatographs
gasoline.
1.5 The values stated in SI units are to be regarded as
3. Terminology
standard. Where non-SI units are provided, they are shown in
3.1 Definitions:
parentheses.
3.1.1 For definitions of terms used in this test method, refer
1.6 This standard does not purport to address all of the
to Terminology D4175.
safety concerns, if any, associated with its use. It is the
3.1.2 This test method makes reference to common gas
responsibility of the user of this standard to establish appro-
chromatographicprocedures,terms,andrelationships.Detailed
priate safety, health, and environmental practices and deter-
definitions of these can be found in Practices E355 and E594.
mine the applicability of regulatory limitations prior to use.
3.1.3 fuel diluent, n—in service oil analysis, is the unburned
1.7 This international standard was developed in accor-
fuel components that enter the engine crankcase causing
dance with internationally recognized principles on standard-
dilution of the oil.
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
3.1.4 fuel dilution, n—the amount, expressed as a
mendations issued by the World Trade Organization Technical
percentage, of engine fuel found in the in-service lubricating
Barriers to Trade (TBT) Committee.
oil.
3.1.5 in-service oil, n—lubricating oil that is present in a
2. Referenced Documents
machine that has been at operating temperature for at least one
2.1 ASTM Standards:
hour.
3.1.6 Marker Peak (MP), n—a marker peak is a chromato-
This test method is under the jurisdiction of ASTM Committee D02 on graphic peak used to differentiate sections of a chromatogram
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
by retention time.
Subcommittee D02.96.02 on Chemistry for the Evaluation of In-Service Lubricants.
3.1.6.1 Discussion—For example, components that elute
Current edition approved Dec. 1, 2022. Published January 2023. Originally
before this marker peak may be considered “fuel,” while
approved in 2013. Last previous edition approved in 2014 as D7593 – 14. DOI:
10.1520/D7593-22.
components that elute after this marker peak would be consid-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
ered “oil.” This marker peak retention time could also serve as
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
thetimingforphysicalchangesinthechromatographicsystem,
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. such as the time to initiate a valve change or a back-flush.
*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
D7593 − 22
3.2 Abbreviations: the column such that no temperature zones below the column
3.2.1 A common abbreviation of carbon compounds is to temperature (cold spots) exist.
designate the number of carbon atoms in the compound. A
7.3 Injector—The preferred injector is a programmable
prefix is used to designate the carbon chain form, while a
pneumatically controlled split capillary injector capable of
subscripted suffix denotes the number of carbon atoms. For
operating continuously at 350 °C and maintaining a split ratio
example, normal eicosane = n-C .
of100/1.Connectionofthecolumntotheinjectorshallbesuch
that no temperature zones below the column temperature (cold
4. Summary of Test Method
spots) exist. It is recommended the injector contain an injector
4.1 A representative aliquot of in-service engine oil is
liner packed with silanized glass wool or equivalent liner and
introduced into a gas chromatograph through a programmable
that the split vent flows through a trap packed with activated
split injector. Carrier gas transports the vaporized aliquot
charcoalbeforereleasingthecarriergastotheatmosphere.The
through the dimethyl polysiloxane bonded phase capillary
programmable injector is preferred for its rapid cooling during
columnwherethehydrocarbonsareseparatedbythechromato-
injector maintenance but an isothermal split injector can be
graphic process. Once the hydrocarbons of interest are sensed
used with slower cooling.
bytheflameionizationdetector,thecarriergaspressure/flowat
7.4 Back-Flush Device—Sufficient injector carrier gas
the head of the column is lowered and an auxiliary gas supply
pressure/flow should be maintained until the marker peak
located at the end of the column is increased. The change in
elutes, marking the point of back-flush. Under the recom-
pressure forces the direction of the carrier gas to reverse
mended conditions within this test method the dodecane
direction and flow back through the injector. The residual
marker peak (for gasoline fuel dilution) should elute within
hydrocarbons on the column are back-flushed out of the
0.6 min and 0.9 min.The eicosane marker peak (for diesel fuel
injector through a charcoal trap and out the split vent. The
dilution) should elute within 1.5 min and 2.1 min. The henei-
detector signal is processed by an electronic data acquisition
cosane marker peak (for biodiesel fuel dilution) should elute
system and the fuel profile is grouped into gasoline, diesel, and
within 1.8 min and 2.4 min. Once the marker peaks elute,
biodiesel. The components are identified by comparing their
reduce injector carrier gas pressure/flow and increase the
retention times to ones identified by analyzing standards under
back-flush carrier gas pressure/flow to allow back-flush of oil
identical conditions. The concentrations of all components are
matrix off the column. Consult instrument vendor for specific
determined by percent area by normalization of the peak areas.
hardware and operational conditions.
5. Significance and Use
7.5 Pneumatic Controllers—The gas chromatograph shall
be capable of maintaining carrier gas pressure constant to
5.1 Some fuel dilution of in-service engine oil is normal
61 % for both the injector and the detector. Most modern gas
under typical operating conditions. However, excessive fuel
chromatographs can control carrier gas in either pressure
dilution can lead to decreased performance, premature wear, or
control mode or flow control mode. The back-flush procedure
sudden engine failure. This test method provides a means of
can be accomplished with either differential pressure or differ-
quantifying the level of fuel dilution, allowing the user to take
ential flow. The basic function is to inject with a high injector
necessary action. This test method does not purport to accu-
carrier and a low auxiliary carrier at the back-flush device so
rately quantify the specific fuel present in the in-service
that a forward flow of carrier is established for chromatogra-
lubricant samples due to limitations associated with the aging
phy. At the desired time, decrease the injector carrier and
and degradation of the fuel in the crankcase. Rather, quantifi-
increase the auxiliary carrier to cause the back-flush. The
cation of diesel fuel is normalized using a simulated aged fuel.
difference in carrier between the injector and the back-flush
6. Interferences device will determine the direction of carrier flow. The reverse
flow shall be higher than the forward flow to cause the
6.1 There may be some overlap of the boiling ranges of
back-flush. Nominal dimensions of all tubing and restrictors
gasoline, diesel, and biodiesel fuels and some new oils could
will affect pressures and flows as well as temperatures in
have light hydrocarbons or formulated additives present from
multiple heated zones such as injector, oven and detector. This
manufacturing. As a result, small deviations in quantitative
analysis utilizes an isothermal oven temperature therefore
analysis could accrue when testing unknown or mixed brands
constant flow control will not improve chromatographic
of in-service engine oil.
throughputorefficiency.Atisothermaloventemperatures,both
pressure and flow will remain constant.
7. Apparatus
7.1 Gas Chromatograph—The following gas chromato- 7.6 Column Conditions—This test method utilizes a fused
silica open tubular column with dimethyl polysiloxane cross
graphic system performance characteristics are required:
bond phase internal coating operating isothermally at 225 °C.
7.2 Detector—This test method requires a flame ionization
7.6.1 Open tubular column with a cross bond 100 % dim-
detector (FID). The detector shall have sufficient sensitivity to
ethyl polysiloxane phase internal coating, 15 m by 0.25 mm ID
detect 0.5 % by mass fuel dilution by area on the data
with a 0.25 µm film thickness.
acquisition device under the conditions recommended in this
test method. The detector shall meet or exceed the specifica- 7.7 Sample Introduction Devices:
tions as detailed in Practice E594. The detector shall be 7.7.1 Microsyringe—A microsyringe is used for sample
capable of operating continuously at 350 °C and connected to introduction capable of precise 0.1 µL injections.
D7593 − 22
7.7.2 Autosampler—Automatic sampling device that repro- 8.2.5 Air, (Warning—Compressed gas under high pres-
ducibly injects 0.1 µL volume is required. The sample intro- sure.)This gas is used to supply oxidant to the flame ionization
duction device should operate in a synchronous manner with detector (FID).
the gas chromatograph.
8.3 Aged Fuel—Aged diesel fuel is prepared by distilling
7.8 Electronic Data Acquisition System—Any data acquisi-
the fuel in accordance with Test Method D86 and stopping the
tion and integration device used for quantification of these distillation process after 10 % of the fuel has been distilled
analyses shall meet or exceed these minimum requirements:
over. The 90 % fuel remaining in the distillation flask is the
7.8.1 Normalizedpercentcalculationsbasedonpeakareaor aged diesel fuel.
peak height.
8.4 Quantification of unknown samples may be affected by
7.8.2 Ability to construct a first order linear regression
the specific sources of fuel used in the calibration. In addition,
calibration curve for up to as many as 10 levels of calibration.
fuel may age and degrade at different rates and by varying
7.8.3 Identification of individual components based on re-
mechanisms once present in the engine’s lubricant. Biodiesel
tention time, named groups, or timed groups.
blends and many ultra-low sulfur diesel fuels contain varying
7.8.4 Baseline corrections for positive or negative sloping
concentrations of fatty acid methyl esters and the specific
baseline.
concentration of biodiesel in any given vehicle’s fuel tank may
7.8.5 Non-resolved peaks separated by perpendicular drop
not be known with certainty. It is beyond the scope of this test
line.
method to require that calibration standards closely match the
7.8.6 Ability to turn on and off integration.
fuel found in the samples. The aging of the fuel standards
7.8.7 Ability to adjust integration stop and start of each
provides an approximation of the actual fuel degradation in
component.
the engine oil and it should be noted that this test method is for
the determination of fuel dilution and not for specific quanti-
8. Reagents and Materials
fication of fuel blends or types.
8.1 Purity of Reagents—Reagent grade chemicals shall be
8.5 Marker Peak Definitions:
used in all tests. Unless otherwise indicated, it is intended that
8.5.1 n-Dodecane 99 % minimum purity (n-C ) Used to
all reagents shall conform to the specifications of the commit-
signify the end boiling range of gasoline.
tee onAnalytical Reagents of theAmerican Chemical Society,
8.5.2 n-Eicosane 99 % minimum purity (n-C ). Used to
where such specifications are available. Other grades may be
used, provided it is pure enough to be used without lessening signify the end boiling range of diesel.
the accuracy of the determination. 8.5.3 n-Heneicosane99 %minimumpurity(n-C ).Usedto
8.1.1 Base Oil—75 mm /s (cSt) @ 40 °C mi
...

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: D7593 − 14 D7593 − 22
Standard Test Method for
Determination of Fuel Dilution for In-Service Engine Oils by
Gas Chromatography
This standard is issued under the fixed designation D7593; 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*
1.1 This test method covers the determination of fuel dilution for in-service engine oil by gas chromatography.
1.2 Analysis can be performed directly by this test method without pretreatment or dilution of the sample.
1.3 There is no limitation for the determination of the dilution range, provided the amount of sample is within the linear range
of the gas chromatograph detector. However, sample dilution can add potential error to the result and may affect the precision
obtained as compared to the values presented in Section 14, which were obtained with no dilution.
1.4 This test method covers a quantitation range up to 10 % (m/m) for diesel and biodiesel, and up to 5 % (m/m) for gasoline.
1.5 The values stated in SI units are to be regarded as standard. Where non-SI units are provided, they are shown in parentheses.
1.6 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.
1.7 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
D3524 Test Method for Diesel Fuel Diluent in Used Diesel Engine Oils by Gas Chromatography
D3525 Test Method for Gasoline Fuel Dilution in Used Gasoline Engine Oils by Wide-Bore Capillary Gas Chromatography
D4175 Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
E355 Practice for Gas Chromatography Terms and Relationships
E594 Practice for Testing Flame Ionization Detectors Used in Gas or Supercritical Fluid Chromatography
E1510 Practice for Installing Fused Silica Open Tubular Capillary Columns in Gas Chromatographs
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
D02.96.02 on Chemistry for the Evaluation of In-Service Lubricants.
Current edition approved Oct. 1, 2014Dec. 1, 2022. Published October 2014January 2023. Originally approved in 2013. Last previous edition approved in 20132014 as
D7593 – 13.D7593 – 14. DOI: 10.1520/D7593-14.10.1520/D7593-22.
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.
*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
D7593 − 22
3. Terminology
3.1 Definitions:
3.1.1 For definitions of terms used in this test method, refer to Terminology D4175.
3.1.2 This test method makes reference to common gas chromatographic procedures, terms, and relationships. Detailed definitions
of these can be found in Practices E355 and E594.
3.1.2 fuel dilution, n—the amount, expressed as a percentage, of engine fuel found in the in-service lubricating oil.
3.1.3 fuel diluent, n—in service oil analysis, is the unburned fuel components that enter the engine crankcase causing dilution of
the oil.
3.1.4 fuel dilution, n—the amount, expressed as a percentage, of engine fuel found in the in-service lubricating oil.
3.1.5 in-service oil, n—lubricating oil that is present in a machine that has been at operating temperature for at least one hour.
3.1.6 Marker Peak (MP), n—a marker peak is a chromatographic peak used to differentiate sections of a chromatogram by
retention time.
3.1.6.1 Discussion—
For example, components that elute before this marker peak may be considered “fuel,” while components that elute after this
marker peak would be considered “oil.” This marker peak retention time could also serve as the timing for physical changes in
the chromatographic system, such as the time to initiate a valve change or a back-flush.
3.2 Abbreviations:
3.2.1 A common abbreviation of carbon compounds is to designate the number of carbon atoms in the compound. A prefix is used
to designate the carbon chain form, while a subscripted suffix denotes the number of carbon atoms. For example, normal eicosane
= n-C .
4. Summary of Test Method
4.1 A representative aliquot of in-service engine oil is introduced into a gas chromatograph through a programmable split injector.
Carrier gas transports the vaporized aliquot through the dimethyl polysiloxane bonded phase capillary column where the
hydrocarbons are separated by the chromatographic process. Once the hydrocarbons of interest are sensed by the flame ionization
detector, the carrier gas pressure/flow at the head of the column is lowered and an auxiliary gas supply located at the end of the
column is increased. The change in pressure forces the direction of the carrier gas to reverse direction and flow back through the
injector. The residual hydrocarbons on the column are back-flushed out of the injector through a charcoal trap and out the split vent.
The detector signal is processed by an electronic data acquisition system and the fuel profile is grouped into gasoline, diesel, and
biodiesel. The components are identified by comparing their retention times to ones identified by analyzing standards under
identical conditions. The concentrations of all components are determined by percent area by normalization of the peak areas.
5. Significance and Use
5.1 Some fuel dilution of in-service engine oil is normal under typical operating conditions. However, excessive fuel dilution can
lead to decreased performance, premature wear, or sudden engine failure. This test method provides a means of quantifying the
level of fuel dilution, allowing the user to take necessary action. This test method does not purport to accurately quantify the
specific fuel present in the in-service lubricant samples due to limitations associated with the aging and degradation of the fuel in
the crankcase. Rather, quantification of diesel fuel is normalized using a simulated aged fuel.
6. Interferences
6.1 There may be some overlap of the boiling ranges of gasoline, diesel, and biodiesel fuels and some new oils could have light
hydrocarbons or formulated additives present from manufacturing. As a result, small deviations in quantitative analysis could
accrue when testing unknown or mixed brands of in-service engine oil.
D7593 − 22
7. Apparatus
7.1 Gas Chromatograph—The following gas chromatographic system performance characteristics are required:
7.2 Detector—This test method requires a flame ionization detector (FID). The detector shall have sufficient sensitivity to detect
0.5 mass % 0.5 % by mass fuel dilution by area on the data acquisition device under the conditions recommended in this test
method. The detector shall meet or exceed the specifications as detailed in Practice E594. The detector shall be capable of
operating continuously at 350 °C and connected to the column such that no temperature zones below the column temperature (cold
spots) exist.
7.3 Injector—The preferred injector is a programmable pneumatically controlled split capillary injector capable of operating
continuously at 350 °C and maintaining a split ratio of 100/1. Connection of the column to the injector shall be such that no
temperature zones below the column temperature (cold spots) exist. It is recommended the injector contain an injector liner packed
with silanized glass wool or equivalent liner and that the split vent flows through a trap packed with activated charcoal before
releasing the carrier gas to the atmosphere. The programmable injector is preferred for its rapid cooling during injector
maintenance but an isothermal split injector can be used with slower cooling.
7.4 Back-Flush Device—Sufficient injector carrier gas pressure/flow should be maintained until the marker peak elutes, marking
the point of back-flush. Under the recommended conditions within this test method the dodecane marker peak (for gasoline fuel
dilution) should elute within 0.6 min and 0.9 min. The eicosane marker peak (for diesel fuel dilution) should elute within 1.5 min
and 2.1 min. The heneicosane marker peak (for biodiesel fuel dilution) should elute within 1.8 min and 2.4 min. Once the marker
peaks elute, reduce injector carrier gas pressure/flow and increase the back-flush carrier gas pressure/flow to allow back-flush of
oil matrix off the column. Consult instrument vendor for specific hardware and operational conditions.
7.5 Pneumatic Controllers—The gas chromatograph shall be capable of maintaining carrier gas pressure constant to 61 % for both
the injector and the detector. Most modern gas chromatographs can control carrier gas in either pressure control mode or flow
control mode. The back-flush procedure can be accomplished with either differential pressure or differential flow. The basic
function is to inject with a high injector carrier and a low auxiliary carrier at the back-flush device so that a forward flow of carrier
is established for chromatography. At the desired time, decrease the injector carrier and increase the auxiliary carrier to cause the
back-flush. The difference in carrier between the injector and the back-flush device will determine the direction of carrier flow. The
reverse flow shall be higher than the forward flow to cause the back-flush. Nominal dimensions of all tubing and restrictors will
affect pressures and flows as well as temperatures in multiple heated zones such as injector, oven and detector. This analysis utilizes
an isothermal oven temperature therefore constant flow control will not improve chromatographic throughput or efficiency. At
isothermal oven temperatures, both pressure and flow will remain constant.
7.6 Column Conditions—This test method utilizes a fused silica open tubular column with dimethyl polysiloxane cross bond phase
internal coating operating isothermally at 225 °C.
7.6.1 Open tubular column with a cross bond 100 % dimethyl polysiloxane phase internal coating, 15 m by 0.25 mm ID with a
0.25 μm film thickness.
7.7 Sample Introduction Devices:
7.7.1 Microsyringe—A microsyringe is used for sample introduction capable of precise 0.1 μL injections.
7.7.2 Autosampler—Automatic sampling device that reproducibly injects 0.1 μL volume is required. The sample introduction
device should operate in a synchronous manner with the gas chromatograph.
7.8 Electronic Data Acquisition System—Any data acquisition and integration device used for quantification of these analyses shall
meet or exceed these minimum requirements:
7.8.1 Normalized percent calculations based on peak area or peak height.
7.8.2 Ability to construct a first order linear regression calibration curve for up to as many as 10 levels of calibration.
7.8.3 Identification of individual components based on retention time, named groups, or timed groups.
D7593 − 22
7.8.4 Baseline corrections for positive or negative sloping baseline.
7.8.5 Non-resolved peaks separated by perpendicular drop line.
7.8.6 Ability to turn on and off integration.
7.8.7 Ability to adjust integration stop and start of each component.
8. Reagents and Materials
8.1 Purity of Reagents—Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all
reagents shall conform to the specifications of the committee on Analytical Reagents of the American Chemical Society, where
such specifications are available. Other grades may be used, provided it is pure enough to be used without lessening the accuracy
of the determination.
8.1.1 Base Oil—75 mm /s (cSt) @ 40 °C mineral oil. Used as a base oil to make the calibration standards and can be used as the
preferred solvent to rinse the syringe. Other base stocks may be used, however alternate materials such as new additized engine
oils may yield a bias in the results.
8.1.2 Carbon Disulfide (CS ), 99+ % pure. (Warning—Extremely flammable and toxic liquid.) One of the solvents that can be
used as a solvent to rinse the syringe.
8.2 Gas—The following compressed gases are utilized for the operation of the gas chromatograph.
8.2.1 Helium, 99.999 %. (Warning—Compressed gas under high pressure.) This gas can be used as carrier gas. Ensure sufficient
pressure for a constant carrier gas flow rate. Precision in this method is based on helium as the carrier gas; however, nitrogen,
hydrogen and argon have been successfully used as the carrier gas.
8.2.2 Nitrogen, 99.999 %. (Warning—Compressed gas under high pressure.) May be used as an alternative carrier gas.
8.2.3 Argon, 99.999 %. (Warning—Compressed gas under high pressure.) May be used as an alternative carrier gas.
8.2.4 Hydrogen, 99.999 %. (Warning—Extremely flammable compressed gas under high pressure.) This gas is used to supply fuel
to the flame ionization detector (FID).
8.2.5 Air, (Warning—Compressed gas under high pressure.) This gas is used to supply oxidant to the flame ionization detector
(FID).
8.3 Aged Fuel—Aged diesel fuel is prepared by distilling the fuel in accordance with Test Met
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