ASTM D6681-08 - 15.10.2008
 
Significance and Use

This is an accelerated engine oil test, performed in a standardized, calibrated, stationary single-cylinder diesel engine that gives a measure of (1) piston and ring groove deposit forming tendency, (2) piston, ring and liner scuffing and (3) oil consumption. The test is used in the establishment of diesel engine oil specification requirements as cited in Specification D 4485 for appropriate API Performance Category C oils (API 1509). The test method can also be used in diesel engine oil development.

 
1. Scope

1.1 This test method covers and 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 standard. No other units of measurement are included in this 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).

1.4 The following is the Table of Contents:

Section

Scope

1

Referenced Documents

2

Terminology

3

Summary of Test Method

4

Significance and Use

5

Apparatus and Installation

6

Intake Air System

6.2.1

Exhaust System

6.2.2

Fuel System

6.2.3

Oil Consumption System

6.2.4

Engine Oil System

6.2.5

Oil Heating System

6.2.5.1

Oil Sample Valve

6.2.5.2

Engine Coolant System

6.2.6

Engine Instrumentation

6.2.7

Reagents and Materials

7

Oil Samples

8

Preparation of Apparatus

9

General Engine Assembly Practices

9.1

Complete Engine Inspection

9.2

Copper Components

9.3

Engine Lubricant System Flush

9.4

Engine Piston Cooling Jets

9.5

Engine Measurements and Inspections

9.6

Cylinder Head

9.7

Valve Guide Bushings

9.8

Fuel Injector

9.9

Piston and Rings

9.10

Cylinder Liner

9.11

Compression Ratio

9.12

Engine Timing

9.13

Engine Coolant System Cleaning Procedure

9.14

Calibration and Standardization

10

Test Cell Instrumentation

10.1

Instrumentation Standards

10.2

Coolant Flow

10.3

Re-calibration Requirements

10.4

Fuel Injectors

10.5

Air Flow

10.6

Intake Air Barrel

10.7

Fuel Filter

10.8

Oil Scale Flow Rates

10.9

Calibration of Test Stands

10.10

Extending Test Stand Calibration Period

10.11

Test Run Numbering

10.13

Humidity Calibration Requirements

10.14

Calibration of Piston Deposit Raters

10.15

Procedure

11

Engine Break-in Procedure

11.1

Cool-down Procedure

11.2

Warm-up Procedure

11.3

Shutdowns and Lost Time

11.4

Periodic Measurements

11.5

Engine Control Systems

11.6

Engine Coolant

11.6.1

Engine Fuel System

11.6.2

Engine Oil Temperature

11.6.3

Exhaust Pressure

11.6.4

Intake Air

11.6.5

Post-Test Procedures

11.7

Piston Ring Side Clearances

11.7.1

Piston Ratings

11.7.2

Referee Ratings

11.7.3

Ring End Gap Increase

11.7.4

Cylinder Liner Wear

11.7.5

Cylinder Liner Bore Polish

11.7.6

Photographs

11.7.7

Calculation and Interpretation of Results

12

Test Validity

12.1

Calculations

12.2

Quality Index

12.2.1

Oil Consumption

12.2.2

Report

13

Forms and Data Dictionary

13.1

Test Validity

13.2

Report Specifics

13.3

Precision and Bias

14

Precision

14.1

Bias

14.1.4

Keywords

15

Annexes

Engine and Parts Warranty

Annex A1

Instrument Locations, Measurements, and Calculations

Annex A2

Cooling System Arrangement

Annex A3

Intake Air Mass Flow Sensor Installation

Annex A4

Fuel System Design and Required Components

Annex A5

Oil System

Annex A6

Exhaust and Intake Barrel Piping

Annex A7

Humidity Probe Installation (Location)

Annex A8

Return Goods Authorization (Claim Form)

Annex A9

Engine Assembly Information

Annex A10

Flushing Instructions and Apparatus

Annex A11

Warm-up, Cool-down and Testing Conditions

Annex A12

Piston and Liner Rating Modifications

Annex A13

Additional Report Forms

Annex A14

Test Report Forms

Annex A15

Appendixes

Various Examples for Reference Purposes

Appendix X1

Safety

Appendix 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