ASTM D7593-13
(Test Method)Standard Test Method for Determination of Fuel Dilution for In-Service Engine Oils by Gas Chromatography
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 and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: D7593 − 13
StandardTest 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 Engine Oils by Gas Chromatography
E355 Practice for Gas ChromatographyTerms and Relation-
1.1 This test method covers the determination of fuel
ships
dilution for in-service engine oil by gas chromatography.
E594 Practice for Testing Flame Ionization Detectors Used
1.2 Analysis can be performed directly by this test method
in Gas or Supercritical Fluid Chromatography
without pretreatment or dilution of the sample.
E1510 Practice for Installing Fused Silica Open Tubular
1.3 There is no limitation for the determination of the Capillary Columns in Gas Chromatographs
dilution range, provided the amount of sample is within the
3. Terminology
linear range of the gas chromatograph detector. However,
3.1 Definitions:
sample dilution can add potential error to the result and may
3.1.1 This test method makes reference to common gas
affect the precision obtained as compared to the values pre-
chromatographicprocedures,terms,andrelationships.Detailed
sented in Section 14, which were obtained with no dilution.
definitions of these can be found in Practices E355 and E594.
1.4 This test method covers a quantitation range up to 10 %
3.1.2 fuel dilution, n—the amount, expressed as a
(m/m) for diesel and biodiesel, and up to 5 % (m/m) for
percentage, of engine fuel found in the in-service lubricating
gasoline.
oil.
1.5 The values stated in SI units are to be regarded as
3.1.3 fuel diluent, n—in service oil analysis, is the unburned
standard. Where non-SI units are provided, they are shown in
fuel components that enter the engine crankcase causing
parentheses.
dilution of the oil.
1.6 This standard does not purport to address all of the
3.1.4 in-service oil, n—lubricating oil that is present in a
safety concerns, if any, associated with its use. It is the
machine that has been at operating temperature for at least one
responsibility of the user of this standard to establish appro-
hour.
priate safety and health practices and determine the applica-
3.1.5 Marker Peak (MP), n—a marker peak is a chromato-
bility of regulatory limitations prior to use.
graphic peak used to differentiate sections of a chromatogram
by retention time.
2. Referenced Documents
3.1.5.1 Discussion—For example, components that elute
2.1 ASTM Standards:
before this marker peak may be considered “fuel,” while
D86 Test Method for Distillation of Petroleum Products at
components that elute after this marker peak would be consid-
Atmospheric Pressure
ered “oil.” This marker peak retention time could also serve as
D3524 Test Method for Diesel Fuel Diluent in Used Diesel
thetimingforphysicalchangesinthechromatographicsystem,
Engine Oils by Gas Chromatography (Withdrawn 2013)
such as the time to initiate a valve change or a back-flush.
D3525 Test Method for Gasoline Diluent in Used Gasoline
3.2 Abbreviations:
3.2.1 A common abbreviation of carbon compounds is to
This test method is under the jurisdiction of ASTM Committee D02 on designate the number of carbon atoms in the compound. A
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
prefix is used to designate the carbon chain form, while a
Subcommittee D02.96.02 on Chemistry for the Evaluation of In-Service Lubricants.
subscripted suffix denotes the number of carbon atoms. For
Current edition approved Dec. 1, 2013. Published January 2014. DOI: 10.1520/
example, normal eicosane = n-C .
D7593-13. 20
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
4. Summary of Test Method
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
4.1 A representative aliquot of in-service engine oil is
the ASTM website.
introduced into a gas chromatograph through a programmable
The last approved version of this historical standard is referenced on
www.astm.org. split injector. Carrier gas transports the vaporized aliquot
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7593 − 13
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 0.6
hydrocarbons on the column are back-flushed out of the
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 and 2.1 min. The heneicosane
detector signal is processed by an electronic data acquisition
marker peak (for biodiesel fuel dilution) should elute within
system and the fuel profile is grouped into gasoline, diesel, and
1.8 and 2.4 min. Once the marker peaks elute, reduce injector
biodiesel. The components are identified by comparing their
carriergaspressure/flowandincreasetheback-flushcarriergas
retention times to ones identified by analyzing standards under
pressure/flow to allow back-flush of oil matrix off the column.
identical conditions. The concentrations of all components are
Consult instrument vendor for specific hardware and opera-
determined by percent area by normalization of the peak areas.
tional 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
7.6 Column Conditions—This test method utilizes a fused
7.1 Gas Chromatograph—The following gas chromato-
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 mass % fuel dilution by area on the data acquisition
with a 0.25 µm film thickness.
device under the conditions recommended in this test method.
7.7 Sample Introduction Devices:
The detector shall meet or exceed the specifications as detailed
in Practice E594. The detector shall be capable of operating 7.7.1 Microsyringe—A microsyringe is used for sample
introduction capable of precise 0.1 µL injections.
continuously at 400°C and connected to the column such that
no temperature zones below the column temperature (cold 7.7.2 Autosampler—Automatic sampling device that repro-
ducibly injects 0.1 µl volume is required. The sample intro-
spots) exist.
duction device should operate in a synchronous manner with
7.3 Injector—The preferred injector is a programmable
the gas chromatograph.
pneumatically controlled split capillary injector capable of
operating continuously at 350°C and maintaining a split ratio 7.8 Electronic Data Acquisition System—Any data acquisi-
tion and integration device used for quantification of these
of100/1.Connectionofthecolumntotheinjectorshallbesuch
that no temperature zones below the column temperature (cold analyses shall meet or exceed these minimum requirements:
7.8.1 Normalizedpercentcalculationsbasedonpeakareaor
spots) exist. It is recommended the injector contain an injector
liner packed with silanized glass wool or equivalent liner and peak height.
that the split vent flows through a trap packed with activated 7.8.2 Ability to construct a first order linear regression
charcoalbeforereleasingthecarriergastotheatmosphere.The calibration curve for up to as many as 10 levels of calibration.
D7593 − 13
7.8.3 Identification of individual components based on re- 8.3 Aged Fuel—Aged diesel fuel is prepared by distilling
tention time, named groups, or timed groups. the fuel in accordance with Test Method D86 and stopping the
7.8.4 Baseline corrections for positive or negative sloping distillation process after 10 % of the fuel has been distilled
baseline. over. The 90 % fuel remaining in the distillation flask is the
7.8.5 Non-resolved peaks separated by perpendicular drop aged diesel fuel.
line.
8.4 Quantification of unknown samples may be affected by
7.8.6 Ability to turn on and off integration.
the specific sources of fuel used in the calibration. In addition,
7.8.7 Ability to adjust integration stop and start of each
fuel may age and degrade at different rates and by varying
component.
mechanisms once present in the engine’s lubricant. Biodiesel
blends and many ultra-low sulfur diesel fuels contain varying
8. Reagents and Materials
concentrations of fatty acid methyl esters and the specific
8.1 Purity of Reagents—Reagent grade chemicals shall be
concentration of biodiesel in any given vehicle’s fuel tank may
used in all tests. Unless otherwise indicated, it is intended that
not be known with certainty. It is beyond the scope of this test
all reagents shall conform to the specifications of the commit-
method to require that calibration standards closely match the
tee onAnalytical Reagents of theAmerican Chemical Society,
fuel found in the samples. The aging of the fuel standards
where such specifications are available. Other grades may be
provides an approximation of the actual fuel degradation in
used, provided it is pure enough to be used without lessening
the engine oil and it should be noted that this test method is for
the accuracy of the determination.
the determination of fuel dilution and not for specific quanti-
8.1.1 Base Oil—75 mm /s (cSt) @ 40°C mineral oil. Used
fication of fuel blends or types.
as a base oil to make the calibration standards and can be used
8.5 Marker Peak Definitions:
as the preferred solvent to rinse the syringe. Other base stocks
8.5.1 n-Dodecane 99 % minimum purity (n-C ) Used to
may be used, however alternate materials such as new ad-
signify the end boiling range of gasoline.
ditized engine oils may yield a bias in the results.
8.5.2 n-Eicosane 99 % minimum purity (n-C ). Used to
8.1.2 Carbon Disulfide (CS ), 99+ % pure. (Warning—
signify the end boiling range of diesel.
Extremely flammable and toxic liquid.) One of the solvents
8.5.3 n-Heneicosane99 %minimumpurity(n-C ).Usedto
that can be used as a solvent to rinse the syringe.
signify the end boiling range of biodiesel.
8.2 Gas—The following compressed gases are utilized for
9. Preparation of Apparatus
the operation of the gas chromatograph.
8.2.1 Helium, 99.999 %. (Warning—Compressed gas un- 9.1 Gas Chromatograph Setup:
der high pressure.) This gas can be used as carrier gas. Ensure 9.1.1 Install the gas chromatograph and place into operation
sufficient pressure for a constant carrier gas flow rate. It is not in accordance with the manufacturer’s instructions. Example
to contain more than 5 mL/m of oxygen and the total amount conditions are listed in Appendix X1.
of impurities are not to exceed 10 mL/m . Precision in this 9.1.2 The injector liner and septum should be periodically
method is based on helium as the carrier gas; however, inspected and replaced if necessary to remove extraneous
nitrogen, hydrogen and argon have been successfully used as deposits and improve injection precision.
the carrier gas. 9.1.3 It is recommended to periodically inspect the split gas
8.2.2 Nitrogen, 99.999 %. (Warning—Compressed gas un- flow through the charcoal trap and replace the trap if necessary
der high pressure.) If used as a carrier gas, it is not to contain toremoveextraneousdepositsandimproveinjectionprecision.
more than 5 mL/m of oxygen and the total amo
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