ASTM D6681-01 - 10.6.2001
 
1. Scope

1.1 This test method is required to evaluate the performance of engine oils intended to satisfy certain American Petroleum Institute (API) C service categories (included in Specification D 4485). It is performed in a laboratory using a standardized high-speed, single-cylinder diesel engine. Piston and ring groove deposit-forming tendency and oil consumption is measured. The piston, the rings, and the liner are also examined for distress and the rings for mobility.

1.2 The values stated in SI units are to be regarded as the standard.

1.3 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. Being an engine test method, this standard does have definite hazards that require safe practices (see Appendix X2 on Safety).

1.3 The following is the Table of Contents:

Section
Scope1
Referenced Documents2
Terminology3
Summary of Test Method4
Significance and Use5
Apparatus and Installation6
Intake Air System6.2.1
Exhaust System6.2.2
Fuel System6.2.3
Oil Consumption System6.2.4
Engine Oil System6.2.5
Oil Heating System6.2.5.1
Oil Sample Valve6.2.5.2
Engine Coolant System6.2.6
Engine Instrumentation6.2.7
Reagents and Materials7
Oil Samples8
Preparation of Apparatus9
General Engine Assembly Practices9.1
Complete Engine Inspection9.2
Copper Components9.3
Engine Lubricant System Flush9.4
Engine Piston Cooling Jets9.5
Engine Measurements and Inspections9.6
Cylinder Head9.7
Valve Guide Bushings9.8
Fuel Injector9.9
Piston and Rings9.10
Cylinder Liner9.11
Compression Ratio9.12
Engine Timing9.13
Engine Coolant System Cleaning Procedure9.14
Calibration and Standardization10
Test Cell Instrumentation10.1
Instrumentation Standards10.2
Coolant Flow10.3
Re-calibration Requirements10.4
Fuel Injectors10.5
Air Flow10.6
Intake Air Barrel10.7
Fuel Filter10.8
Oil Scale Flow Rates10.9
Calibration of Test Stands10.10
Extending Test Stand Calibration Period10.11
Test Run Numbering10.12
Humidity Calibration Requirements10.13
Calibration of Piston Deposit Raters10.14
Procedure11
Engine Break-in Procedure11.1
Cool-down Procedure11.2
Warm-up Procedure11.3
Shutdowns and Lost Time11.4
Periodic Measurements11.5
Engine Control Systems11.6
Engine Coolant11.6.1
Engine Fuel System11.6.2
Engine Oil Temperature11.6.3
Exhaust Pressure11.6.4
Intake Air11.6.5
Post-Test Procedures11.7
Piston Ring Side Clearances11.7.1
Piston Ratings11.7.2
Referee Ratings11.7.2.1
Ring End Gap Increase11.7.3
Cylinder Liner Wear11.7.4
Cylinder Liner Bore Polish11.7.5
Photographs11.7.6
Calculation and Interpretation of Results12
Test Validity12.1
Calculations12.2
Quality Index12.2.1
Oil Consumption12.2.2
Report13
Forms and Data Dictionary13.1
Test Validity13.2
Report Specifics13.3
Precision and Bias14
Precision14.1
Bias14.2
Keywords15
Annexes
Engine and Parts WarrantyAnnex A1
Instrument Locations, Measurements, and CalculationsAnnex A2
Cooling System ArrangementAnnex A3
Intake Air Mass Flow Sensor InstallationAnnex A4
Fuel System Design and Required ComponentsAnnex A5
Oil SystemAnnex A6
Exhaust and Intake Barrel PipingAnnex A7
Humidity Probe Installation (Location)Annex A8
Return Goods Authorization (Claim Form)Annex A9
Engine Assembly InformationAnnex A10
Flushing Instructions and ApparatusAnnex A11
Warm-up, Cool-down and Testing ConditionsAnnex A12
Piston and Liner Rating ModificationsAnnex A13
Additional Report FormsAnnex A14
Test Report FormsAnnex A15
Test Report Data DictionaryAnnex A16
Appendixes
Various Examples for Reference PurposesAppendix X1
SafetyAppendix X2
 
2. Referenced Documents

D97-17b(2022)

Standard Test Method for Pour Point of Petroleum Products (Includes all amendments and changes 11/29/2022).

D130-26

Standard Test Method for Corrosiveness to Copper from Petroleum Products by Copper Strip Test

D86-23ae2

Standard Test Method for Distillation of Petroleum Products and Liquid Fuels at Atmospheric Pressure (Includes all amendments and changes 11/4/2024).

D93-26

Standard Test Methods for Flash Point by Pensky-Martens Closed Cup Tester

D235-22

Standard Specification for Mineral Spirits (Petroleum Spirits) (Hydrocarbon Dry Cleaning Solvent)

D445-26

Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and Calculation of Dynamic Viscosity)

D482-25

Standard Test Method for Ash from Petroleum Products

D5185-26

Standard Test Method for Multielement Determination of Used and Unused Lubricating Oils and Base Oils by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES)

D5862-09

Standard Test Method for Evaluation of Engine Oils in Two-Stroke Cycle Turbo-Supercharged 6V92TA Diesel Engine (Withdrawn 2009)

D6202-02

Standard Test Method for Automotive Engine Oils on the Fuel Economy of Passenger Cars and Light-Duty Trucks in the Sequence VIA Spark Ignition Engine (Withdrawn 2009)

D6593-18e1

Standard Test Method for Evaluation of Automotive Engine Oils for Inhibition of Deposit Formation in a Spark-Ignition Internal Combustion Engine Fueled with Gasoline and Operated Under Low-Temperature, Light-Duty Conditions (Includes all amendments and changes 6/22/2022).

D7422-25

Standard Test Method for Evaluation of Diesel Engine Oils in T-12 Exhaust Gas Recirculation Diesel Engine

API 1509

ASTM Deposit Rating Manual 20

(formerly CRC Manual 20) For Stock #TMCMNL20, visit the ASTM website, www.astm.org, or contact ASTM International Customer Service at service@astm.org.

E29-22

Standard Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications

G40-25a

Standard Terminology Relating to Wear and Erosion (Includes all amendments and changes 12/8/2025).

D664-24

Standard Test Method for Acid Number of Petroleum Products by Potentiometric Titration

D4739-26

Standard Test Method for Base Number Determination by Potentiometric Hydrochloric Acid Titration

D3524-14(2020)

Standard Test Method for Diesel Fuel Diluent in Used Diesel Engine Oils by Gas Chromatography

D4175-24e2

Standard Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants (Includes all amendments and changes 6/9/2026).

D4052-22

Standard Test Method for Density, Relative Density, and API Gravity of Liquids by Digital Density Meter

D4485-24

Standard Specification for Performance of Active API Service Category Engine Oils

D3227-24

Standard Test Method for (Thiol Mercaptan) Sulfur in Gasoline, Kerosine, Aviation Turbine, and Distillate Fuels (Potentiometric Method)

D2274-14(2019)

Standard Test Method for Oxidation Stability of Distillate Fuel Oil (Accelerated Method)

D2425-23

Standard Test Method for Hydrocarbon Types in Middle Distillates by Mass Spectrometry

D2500-23

Standard Test Method for Cloud Point of Petroleum Products and Liquid Fuels

D2622-26

Standard Test Method for Sulfur in Petroleum Products by Wavelength Dispersive X-ray Fluorescence Spectrometry

D2709-22

Standard Test Method for Water and Sediment in Middle Distillate Fuels by Centrifuge

D524-15(2025)e1

Standard Test Method for Ramsbottom Carbon Residue of Petroleum Products (Includes all amendments and changes 8/11/2025).

D613-26

Standard Test Method for Cetane Number of Diesel Fuel Oil

D1319-26

Standard Test Method for Hydrocarbon Types in Liquid Petroleum Products by Fluorescent Indicator Adsorption