ASTM D7320 Standard Test Method for Evaluation of Automotive Engine Oils in the Sequence IIIG, Spark-Ignition Engine
12. Determination of Test Results
12.1 This section describes techniques used to evaluate oil performance with respect to oxidation (viscosity increase), wear (camshaft and lifter), piston deposits, ring sticking, and oil consumption.

12.2 Engine Disassembly - Disassemble the engine according to the following instructions, in preparation for inspection, rating, and measurement:
12.2.1 Plan the disassembly so that the parts to be rated for sticking, deposits, and plugging (pistons and rings) are removed from the engine within 12 h of the completion of the oil level.

12.2.2 Remove the components from the top of the engine in order to gain access to the cylinder bores.

12.2.3 Remove the carbon deposits from the top portion of the cylinder walls, above the top compression ring travel, before removing the pistons from the engine.

12.2.4 Disassemble the remainder of the engine.

12.3 Preparation of Parts for Rating of Sticking, Deposits, and Plugging - Prepare the specified parts for rating according to the following instructions:
12.3.1 Check all piston rings for freedom of movement in the grooves when removing the pistons from the engine. See 12.4.1 through 12.4.1.1.
12.3.1.1 Determine which rings are hot-stuck or cold-stuck (see 3.1.12 and 3.1.5, respectively, for definitions of hot-stuck and cold-stuck rings) and record the piston number and ring identification (for example, piston No.3, top ring) for such rings on Form 8, Summary of Oil Ring Land Deposit Rating, in standardized report form set (see Annex A8). Record the total number of hot-stuck rings on Form 4, Test Result Summary, in the standardized report form set (see Annex A8).

12.3.2 At time of disassembly, remove all piston rings that are free. Leave any stuck rings (includes pinched rings; see 3.2.9) in place. Apply a rating of 100 % heavy carbon in the groove to any piston groove that cannot be rated, due to the presence of a stuck ring.

12.3.3 If the piston deposits cannot be rated immediately after the pistons are removed from the engine, store the pistons in a desiccator for no longer than 72 h from end of test before rating. Do not wipe the pistons before storing them, see 12.4.

12.4 Piston Deposit Ratings - Rate the pistons for piston skirt varnish as well as deposits on the ring lands, under-crown area, and in the ring grooves.
12.4.1 Gently wipe off excess oil from the piston skirts with a soft cloth.
12.4.1.1 Do not apply any chemicals or build-up oil to the pistons prior to rating them for deposits.

12.4.2 Rate each piston top groove, 2nd groove, oil ring groove, 2nd land, and undercrown area (where the horizontal and vertical planes meet) for deposits using ASTM Deposit Rating Manual No. 20 rating techniques and breakdown methods. Carbon deposit ratings will consist of only two levels: Heavy (0.00 merit value) or Light (0.75 merit value).
12.4.2.1 Perform these ratings in a rating booth, using a 20-segment piston-rating cap, a piston rating stand, and a 22 W circular rating lamp.

12.4.2.2 The undercrown area to be rated is defined as the area on the undercrown of the piston that demarcated by casting lines on the piston itself, which resembles a common adhesive bandage. Rate only the area on the underside of the piston crown. Do not rate any parts on the inside surface of the piston skirts as part of the undercrown rating.

12.4.2.3 Report any unusual deposits observed in the comments Section of Summary of Piston Deposits in standardized report form set (see Annex A8).

12.4.3 If multiple ratings are deemed necessary of a given part or parts, consensus rating may be used according to the following:
12.4.3.1 The raters shall be from the laboratory in question, no outside raters may be used unless requested and directed through the Sequence IIIG Surveillance Panel.

12.4.3.2 No averaging of ratings is permitted.

12.4.3.3 Report only one rating value, which is agreed to by the involved raters.

12.4.3.4 All raters of Sequence IIIG engine pistons shall attend an ASTM Light Duty Deposit Rating Workshop every 12 months +/- 30 days and produce data that meet the TMC definitions of Blue, Red, or White for piston deposits. If a rater is unable to meet this requirement, the rater can continue to rate Sequence IIIG pistons after the completion of the workshop for a grace period of 45 days and can follow the procedure described in 12.4.3.5 to generate data that meet the TMC definitions of Blue, Red, or White.

12.4.3.5 A rater who is unable to meet the requirement in 12.4.3.4 can schedule a visit to the TMC to generate data on ASTM Light Duty Deposit Rating Workshop pistons and receive an assessment of rating performance compared to data collected at recent workshops. Visits to the TMC will be scheduled based on availability of parts.

12.4.3.6 The TMC selects a minimum of six pistons from a collection of workshop parts for the rater to rate piston deposits. The TMC provides rating booths and lights, but the rater is responsible for providing any necessary rating aids. The TMC analyzes the data and determine if the requirement in 12.4.3.4 has been met. If the requirement in 12.4.3.4 has not been met, any time remaining in the 45 day grace period is forfeited.

12.4.3.7 A second attempt to generate rating data at the TMC is permitted only after the rater receives training from an experienced industry rater. The experienced industry rater shall verify to the TMC, in writing, that the rater training has taken place. No more than two attempts are permitted between ASTM Light Duty Deposit Rating Workshops.

12.4.4 Average each individual piston (thrust side and anti-thrust side) for inclusion in the Weighted Piston Deposit (WPD) results.

12.4.5 Calculate the average of the six oil ring land (land 3) ratings and record this as the average oil ring land deposits on Form 8, Summary of Oil Ring Land Deposit Rating (ORLD), and on Form 4, Test Results Summary, in standardized report form set (see Annex A8).

12.4.6 Weighted Piston Deposit Rating (WPD) - This weighted piston rating is comprised of skirt varnish, top groove, 2nd groove, oil ring groove, under-crown, 2nd land, and 3rd land.
12.4.6.1 Calculate the Weighted Piston Deposit (WPD) result for each individual piston is calculated using the following weighting factors:
Piston Under-crown: 10 %
2nd Land: 15 %
3rd Land (ORLD): 30 %
Piston Skirts (APV): 10 %
Top Groove: 5 %
2nd Groove: 10 %
Oil Ring Groove: 20 %

12.4.6.2 Calculate the Weighted Piston Deposit result for each piston by multiplying the rated result for each piston part by the weighting factor in 12.4.6.1 (in decimal form) to determine a weighted rating for that piston part. The Weighted Piston Deposit result is the sum of the weighted ratings for the individual piston parts.

12.4.6.3 The Weighted Piston Deposit (WPD) result for the test is calculated by a simple average of the six individual piston WPD ratings.

12.5 Post-Test Camshaft and Lifter Wear Measurements - Measure the wear of the camshaft lobes and lifters to the nearest 0.001 mm. Refer to Practice E29 for any needed rounding; use the rounding-off method. Proceed according to the following procedure:
12.5.1 Clean the camshaft lobes and lifters with degreasing solvent; blow-dry them with clean, dry shop air.

12.5.2 Store the camshaft and lifters in a temperature-controlled room, before making dimensional measurements, for at least 90 min to ensure temperature stabilization. The temperature of the post-test measurement room shall be within 3 °C of the temperature of the pre-test measurement room.

12.5.3 Make the camshaft measurement using Mitutoyo Snap Gauge, model 201-152, and a Mitutoyo Digital Indicator, model 543-252B, to measure the camshaft lobes. Make the lifter measurement with a digital indicator equipped with a Mitutoyo 4.3 mm flat tip, model 131-259 mounted in a indicator stand. Equip the indicator stand with a V-block that is rigidly mounted to the base and locates the lifter with its center axis in line with the digital indicator.
12.5.3.1 Use dimensional measuring equipment accurate to 0.01 mm. Before each measurement session, use standards traceable to the National Institute of Standards and Technology (NIST), to ensure measuring equipment accuracy. Include standards having length values within 1.3 mm of the typical lifter and lobe measurements taken. Use the same equipment and standards for post-test measuring as were used for pre-test measuring. If a calibration shift between pre-test and post-test measurements is detected, evaluate the shift to determine its effect on the wear measurements. Record the results of the evaluation, and any corrective action taken.

12.5.4 The same person shall measure the camshaft and the lifters used in a given test if the measurement equipment utilized is operator-sensitive (that is, if the micrometer has operator-determined spindle pressure).

12.5.5 When measuring the camshaft and the lifters, take precautions to prevent any influence of body heat on the measurements.

12.5.6 Measure the maximum dimension of each camshaft lobe, transverse to the camshaft axis. This dimension is at the rear edge of all lobes (lobes are numbered from the front to the rear of the camshaft).

12.5.7 Measure the length of the lifters at the center of the lifter foot.

12.5.8 Calculate the wear for each camshaft lobe and lifter by subtracting the after-test measurement from the before-test measurement.
12.5.8.1 Due to varnish accumulations on camshaft lobes of high wear resistant oils, post-test measurements may indicate a larger numeric value than pre-test measurements. In this situation, the end of test calculation equates to a negative value. All negative values shall be overridden and entered as 0.000 mm wear for all calculations when determining post-test results.

12.5.9 Calculate the cam-plus-lifter wear by adding the values obtained in 12.5.8. Record the results on Form 7, Valve Lifter and Camshaft Wear Results, in standardized report form set (see Annex A8). Store the cam and lifters; the method and length of time for storage are left up to the laboratory.

12.5.10 Determine the maximum, minimum, and average camshaft-lobe, valve-lifter, and cam-plus-lifter wear. Record the values on Form 7, Valve Lifter and Camshaft Wear Results, in standardized report form set (see Annex A8).

12.6 Viscosity Test - Determine the viscosity of a sample of the fresh test oil and of the nine test samples by analysis according to the following instructions:
12.6.1 Do not filter the samples.

12.6.2 Use Test Method D445.

12.6.3 Use either the Cannon-Fenske Routine Viscometer of the Ostwald Type for Transparent Liquids or the Cannon-Fenske Opaque Viscometer of the Reverse-Flow Type for Transparent and Opaque Liquids.

12.6.4 Conduct the measurement at 40 °C.

12.6.5 Record the results (see Annex A8).

12.6.6 Critically examine the relationship of the viscosity of the initial oil sample to that of the new oil. The viscosity of the initial sample can legitimately be as much as 10 mm2/s less than that of the new oil, because of permanent shearing effects. If the difference is greater than 10 mm2/s, explore possible causes such as failure to purge the oil sample line [removing the 473 mL purge sample] prior to withdrawing the 237 mL analysis sample, or an excessive amount of build-up oil in the system.

12.6.7 Calculate the change in viscosity in mm2/s, from the value for the initial sample, for the last five samples. Record the changes on Form 6, Used Oil Analysis Results, in standardized report form set (see Annex A8). Record the final percent viscosity increase on Form 4, Test Result Summary, in standardized report form set (see Annex A8).

12.6.8 Calculation instructions for special cases related to percent viscosity increase:
12.6.8.1 Instructions for calculating and reporting results if the Final Original Units Result on Form 4 (see Annex A8) for percent viscosity increase is zero or negative.
(1) The minimum result that will be considered for the percent viscosity increase is 0.1 %. Substitute 0.1 % for the original unit result and complete the calculations on Form 4 (see Annex A8). A notation is required in the Other Comments & Outliers Section of Form 13 (see Annex A8) indicating that the Original Units Result has been modified for a special case. 12.6.8.2 Instructions for calculating and reporting results of the Viscosity Result on Form 6 (see Annex A8) for Viscosity Increase Data is Too Viscous to Measure (TVTM).
(2) The maximum kinematic viscosity result reported will be 8000 mm2/s using either equipment noted in 12.6.3, use a tube size of 500 or less. If the measured viscosity is 8000 mm2/s using tube size 500, this will be considered the maximum reportable viscosity. Report 8000 mm2/s on Form 6 (see Annex A8) for entry in the column listed as Viscosity and use this value for the calculating Change and Percent. (This will provide consistent TVTM data for reporting purposes and it also expands the maximum viscosity to fill the space allowed by the Data Dictionary.)
(3) Complete the calculations on Form 4 (see Annex A8) for percent viscosity increase using the percent value for the final drain from Form 6 except that the Severity Adjustment (SA) displayed and used for percent viscosity increase calculations will be set to zero (0). A notation is required in the Other Comments & Outliers Section of Form 13 (see Annex A8) indicating that the Severity Adjustment has been modified for a special case.

12.7 Testing Oil Samples for Wear Metals - Use Test Method D5185 to perform Inductively Coupled Plasma Optical Emission Spectrometry (ICP) Analysis on the initial and all 20 h oil samples for iron, copper, and lead concentrations in the oil. Report the results of the ICP Analysis on these three metals on Form 6 (see Annex A8).

12.8 Blowby Flow Rate Measurements - Plot blowby flow rate measurements on Form 10, Blowby Results & Plot, in standardized report form set (see Annex A8).

12.9 Oil Consumption Computation - Compute the oil consumption for the test as follows:
12.9.1 See Fig.A12.1 for the oil-consumption calculation equation.

12.9.2 Determine the total fresh oil added to the engine during the initial oil leveling run and 20 h test periods in of Fig.A12.1. Enter the total in the End-Of-Test Total column on Fig.A12.1 in position a.

12.9.3 Determine the total amount of oil discarded during the 100 h test period in Fig.A12.1. Enter the total in the end-of-test total column on Fig.A12.1 in position b.

12.9.4 Determine the oil level in millilitres at the end of the test, in Fig.A12.1. Enter the number in the end-of-test total column on Fig.A12.1 in position c.

12.9.5 Add the values determined in 12.9.2 and 12.9.4, and subtract the value determined in 12.9.3. Subtract 236 mL (the final oil sample, which is not replaced with new oil) from the value computed above and enter the remainder, which is the amount of oil consumed in the test, in the blank for total oil consumption in the Fig.A12.1.

12.9.6 To determine the computed millilitres low value for the 100 h oil level only, subtract 708 mL from the value determined in 12.9.4. This is done to account for samples not returned (236 mL analysis sample and 472 mL of new oil) to the engine as in previous oil levels. This value is entered on Form 5 of the test report (see Annex A8).

12.9.7 For non-reference oils, the test results are considered non-interpretable for the purpose of Multiple Test Acceptance Criteria (MTAC) if the oil consumption at the end of test exceeds 4.89 L.

12.10 Photographs of Test Parts - Take color photographs of the test parts for inclusion in the test report, as follows:
12.10.1 Photograph pistons after completing all ratings.

12.10.2 Do not coat the pistons with build-up oil (for preservation) before the photographs are taken. Do not reinstall piston rings.

12.10.3 Photograph all six piston thrust sides in one shot. Piston labels are not required (see 12.10.7).

12.10.4 Photograph all six piston anti-thrust sides in one shot. Piston labels are not required (see 12.10.7).

12.10.5 Size the final piston photographs for inclusion in the test report so that the overall piston height is not less than 5 cm, but small enough that three photographs can be mounted in a column on the 28 cm dimension of a 22 cm by 28 cm sheet of paper.

12.10.6 Assemble the photographs on two pages, with the thrust side photographs on one page, and the anti-thrust photographs on the other page.

12.10.7 Mount the photographs on each of the two pages with the reciprocating axes of the pistons parallel to the 28 cm dimension of the page. Arrange the photographs in two vertical columns of three each, with the No.1 piston in the upper left corner of the page, No.2 piston in the upper right corner, No.3 piston in the center of the left column, and so forth.

12.11 Retention of Representative Test Parts - Retain for at least 6 months all camshafts and lifters.

12.12 Severity Adjustments - Calculate severity adjustments (SA) for results of non-reference engine oil tests. Use the control chart technique (see 12.13.1) for determining the laboratory bias for percent viscosity increase, piston skirt varnish, and weighted piston deposits. Enter the adjustments on Form 4, Test Result Summary, in standardized report form set (see Annex A8).
12.12.1 Download the document, "The Lubricant Test Monitoring System", from internet website (http://www.dgaequipment.com/) for information on the Sequence IIIG Test Control Chart Technique For Developing And Applying Severity Adjustments (SA); a printed copy can be obtained from the TMC.

12.13 Determination of Operational Validity - Determine and document the operational validity of every Sequence IIIG test conducted, according to the following:
12.13.1 Complete the report forms to substantiate that the test stand, engine build-up, installation of the engine on the test stand, and the test operation conformed to the procedures specified in this test method.

12.13.2 Inspect the test records for instances of downtime (excluding the initial oil level run of the test), and record any such instances on Form 13, Downtime and Outlier Report Form, in standardized report form set (see Annex A8). When performing each 20 h oil level adjustment, identify as downtime any time in excess of 55 min from the time when the engine ramps down until the test is back on test operating conditions. Enter the total downtime on Form 13, Downtime and Outlier Report Form, in standardized report form set (see Annex A8). If the total downtime exceeds 24 h, note on Form 1, in standardized report form set (see Annex A8) that the test is invalid.

12.13.3 If the end of test quality-index value is below 0.000, conduct an engineering review of the test operations. The test laboratory shall conduct the engineering review of reference oil tests and report its findings to the Test Monitoring Center. If needed, additional industry experts may be consulted. Document the results of the engineering review.