ASTM D5302 Standard Test Method for Evaluation of Automotive Engine Oils for Inhibition of Deposit Formation and Wear in a Spark-Ignition Internal Combustion Engine Fueled with Gasoline and Operated Under Low-Temperature, Light-Duty Conditions
13. Interpretation of Results
13.1 Parts Rating Area - Environment:
13.1.1 Ensure that the ambient atmosphere of the parts rating area is reasonably free of contaminants, and that the temperature is maintained at 75 +/- 5°F (24 +/- 3°C). When a rater seeks advice from another rater, report the rating as a consensus rating in the final report. Do not use raters from outside sources (other laboratories) for consensus ratings and do not average these ratings. Include independent ratings in the supplemental pages as information only.

13.1.2 Rate all engine parts except the pistons, RAC, and cylinder block under cool white fluorescent lighting exhibiting approximately 4500 K color temperature, and an illumination level of 350 to 500 fc (3800 to 5400 lx). All background and adjacent surfaces shall be flat white.

13.1.3 Rate pistons and RACs against a white background using white fluorescent bulbs and a 100 % white deflector. Maintain the illumination level between 350 and 600 fc (3800 to 6500 lx), and measure the illumination level 14 in. (360 mm) from the desk top. Provide a 15-W bore light with a cool white fluorescent tube for the cylinder wall varnish rating.

13.2 Sludge Ratings:
13.2.1 Rate the following parts for sludge deposits: RAC, valve deck, cylinder block, camshaft baffle, front seal housing, and oil pan. Use the rating locations identified on the rating worksheets (see Annex A6). Determine the ratings using the techniques detailed in CRC Manual No.12. Adjust RAC sludge on candidate tests for laboratory severity in accordance with Annex A12.

13.2.2 Average Sludge (Unweighted Average of All Six Parts):
13.2.2.1 Use the self-weighting procedure detailed as follows to determine the sludge rating for each part. Adjust the average sludge on non-reference tests for laboratory severity in accordance with Annex A12.
(a) Determine the sludge depth at each of the sites shown on rating worksheets. A site is defined as a 0.75-in. (19.1-mm) diameter circle.
(b) Determine an interpolated sludge value for a designated site that exhibits more than one level of sludge depth within this area. This value is generated by multiplying each rated value's volume factor by the percentage of area covered, totaling these volume factor percentages, and comparing the total to the values given in Table 8 to determine the rating for the site. As an example, if a site was determined to be 50 % A and 50 % E, the calculation would be: 50 % of the average sludge depth factor for A (or 1.0), plus 50 % of the average sludge depth factor for E (or 16.0); that is: ([0.5 x 1.0 = 0.5] + [0.5 x 16.0 = 8] = 8.5), and the calculated site sludge depth would be a D. In the event that there are areas where it is apparent that deposits had formed, but are no longer adhering to the part, the rating site is the closest point to the designated point that will eliminate the voided area from the 0.75-in. (19.1-mm) rating area.
(c) Add the total rating checks made for each line on the appropriate worksheets. These shall equal 10 or 20, depending on the part that is rated.
(d) Multiply the total rating checks made on each line by ten or five, respectively (refer to (c)), to obtain the percent covered by the rated sludge depth. The grand total shall equal 100 %.
(e) Convert the percent covered by the rated sludge depth at each location to a volume factor using the procedure shown in CRC Manual No. 12.
(f) Add the volume factors on each line to determine the total volume factor. Use CRC Manual No.12 to convert the total volume factor to the sludge merit rating.

13.2.2.2 Flaky, Bubbly Sludge Deposits - Since the occurrence of flaky, bubbly sludge deposits is thought to have a possible detrimental effect on long-term engine lubrication system performance, document the occurrence of this type of deposit in the Supplemental Operational Data section of the Final Test Report. The type of information to be recorded is the engine part(s) where this type of deposit was observed. Suggested wording is as follows: Approximately 6 % of the RAC was found to exhibit flaky, bubbly sludge deposits.

13.3 Varnish Ratings:
13.3.1 Preparation of Parts - Rate the following parts for varnish deposits: piston skirts, camshaft baffle, oil pan, rocker arm cover, and cylinder walls. Perform the varnish ratings after the sludge ratings are completed. The rating locations and dimensions shall conform with the locations and dimensions detailed on the rating worksheets (see Annex A6). Avoid disturbing sludge deposits when the parts are being prepared for varnish ratings. Heavy sludge can be removed from a varnish rating area with a 1-in. (25-mm) rubber spatula prior to wiping. Wipe all parts firmly with wiping materials specified in CRC Manual No.14. Firmly rub all wiping areas in the same direction until the surface is dry and free of sludge (until no more deposit is present on the wiping material after wiping).

13.3.2 Average Varnish (Unweighted Average of the First Five Parts) - Use the procedure detailed as follows to determine the varnish rating of each part:
13.3.2.1 Rate any areas where varnish deposits have been altered during disassembly or sludge removal in accordance with deposits on the surrounding non-altered areas. Do not rate altered areas as clean.

13.3.2.2 Determine varnish ratings of all parts except pistons by comparison of the deposit on the rating location with color chips. The piston photographs shown in CRC Manual No.14 shall be used to determine the varnish ratings on the pistons.

13.3.2.3 Determine the average varnish rating over each area specified in the rating worksheets. Adjust piston skirt varnish ratings on non-reference tests for laboratory severity in accordance with Annex A12.

13.3.2.4 Determine the average varnish rating of the entire part.

13.4 Clogging:
13.4.1 Oil Screen Clogging - Determine the percentage of the total screen opening that is obstructed with sludge and debris.
13.4.1.1 Flexible, transparent rating aids can be made for different surface areas so that when compared to the test screen's surface, a more accurate determination of surface clogging is possible. These are made of thin, colored transparent plastic cut into circles equivalent in area to 20, 10, and 5 % (1.5, 1.125, and 0.75 in. [38.1, 28.6, and 19.1 mm] in diameter, respectively) of the 9.5 in.2 (6130 mm2) flow surface.

13.4.1.2 If there is any question concerning whether the screen is covered with oil or sludge, blow lightly on the screen (see CRC Manual No.12). Note an analysis of deposits identified as debris in the Supplemental Operational Data.

13.4.2 Oil Ring Clogging - Determine the percentage of slot clogging for each oil ring in accordance with the procedure detailed in CRC Manual No.12. Calculate and record the average clogging for all four rings.

13.4.3 PCV Valve Clogging - Determine the percent clogging of the PCV valve that is used during the last 48 h of the test, in accordance with the following procedure:
13.4.3.1 Measure the PCV valve flow rate at differential pressures from 8 and 18 in. Hg (13.5 and 60.8 kPa). Calculate the percent clogging in accordance with the following equation:
PCV valve clogging, % = (I - F)/I x 100
where:
I = initial flow rate, and
F = final flow rate.

13.4.3.2 If any of the PCV valves have been replaced before the scheduled replacement interval, calculate and report the PCV valve clogging for all of the PCV valves. Report the percent clogging of the last valve on the Ratings and Measurements Page.

13.4.4 Camshaft Lobe Orifice Clogging - Determine the camshaft lobe orifice clogging with the camshaft lobe orifice flow rate device (see 7.5.3 and Figs. A3.32 and A3.33) in accordance with the following procedure:
13.4.4.1 Connect the apparatus to a source of compressed air.

13.4.4.2 Adjust the two pressure regulators until the probe pressure is 10 in. water (2.5 kPa).

13.4.4.3 Calibrate the apparatus by measuring the flow rate when the probe pressure is 10.0 +/- 0.2 in. water (2.49 +/- 0.05 kPa) and the probe is firmly seated in the calibration lobe orifice (clean orifice) with the probe pressure adjusted to 10.0 +/- 0.2 in. water (2.49 +/- 0.05 kPa). Record the flow rate as Baseline Flow Rate on the rating worksheet.

13.4.4.4 Firmly seat the probe in each lobe hole, adjust the probe pressure to 10 +/- 0.2 in. water (2.49 +/- 0.05 kPa), and record the flow rate.

13.4.4.5 Calculate and record the percent flow rate reduction in accordance with the following equation:
camshaft lobe orifice flow rate reduction, % = (I - F)/I x 100
where:
I = initial flow rate, and
F = final flow rate.

13.4.4.6 Record the number of clogged camshaft lobe orifices. Clogged orifices are defined as orifices having a flow rate reduction greater than 80 %.

13.5 Sticking:
13.5.1 Compression Rings - Record the number of stuck compression rings. Definitions to classify the degree and type of sticking are detailed in Section 3. List only hot stuck compression rings on the Ratings and Measurements Summary page. Denote hot or cold stuck rings on the Supplementary Operational Data page and include the ring location (top or second) and the piston number.

13.5.2 Hydraulic Lifter Plungers - Record the number of hydraulic lifter plungers that are completely stuck in the lash adjuster bodies. Note partially stuck plungers on the final engine inspection sheet.

13.6 Wear Measurements:
13.6.1 Camshaft Lobe Wear - Measure and record the heel-to-toe measurement of each camshaft lobe at the maximum lift point using a device reading directly in micrometres, with an accuracy of at least +/- 3 µm. Calculate the wear based on the before-test measurements.

NOTE 11 - The + 0.14 adjustment replaces the + 0.24 adjustment. Do not apply both adjustments.

13.6.1.1 For reference oil tests completed on or after May 16, 1996, add 1.451 to the transformed average cam wear result and 1.693 to the transformed maximum cam wear result. Until a reference oil test is conducted on or after May 16, 1996, do not add 1.451 and 1.693 to average and maximum cam wear non-reference oil test results. Adjust wear results for laboratory severity in accordance with Annex A12.

13.6.2 Rocker Arm Wear - Wash the rocker arms with aliphatic naphtha. Wash the rocker arms with ethyl acetate and allow the rocker arms to air dry. Weigh the rocker arms and calculate the weight loss based on the before-test weights.

13.6.3 Connecting Rod Bearing Wear - Wash the bearings in aliphatic naphtha. Dip the bearings in pentane and allow the bearings to air dry. Measure the bearing weights. Calculate the weight loss based on the before-test measurements. The bearing weight loss is the total loss for two halves of each bearing.

13.6.4 Piston Ring Gap Increase - Clean the ring ends thoroughly and measure the ring gap after the rings have been installed in the block (see 7.8, 11.2). Calculate the ring gap increase. Compensate for any ring gap adjustments made during the test.

13.6.5 Cylinder Bore Wear - Measure the transverse bore wear at the top, middle, and bottom of the second compression ring travel, using the technique specified in 7.8.9.5 (a). Measure the bores with both stress plates installed. Calculate wear based on the before-test versus after-test measurements.

13.7 Used Oil Analysis:
13.7.1 Perform the following analyses on the used oil samples from hours 0 (new oil), 12, 108, 204, and 288: Iron content, ppm; copper content, ppm; silicon content, ppm; and kinematic viscosity at 40°C, cSt (in accordance with Test Method D445).

13.7.2 Fuel Dilution - Determine the fuel dilution, percent mass, by gas chromatography (see Test Method D3525, with the following modifications) on the used oil samples from hours 12, 108, 204, and 288:
13.7.2.1 Use C16 in place of C14 for the internal standard (1-L injector volume).

13.7.2.2 Presume that all components lighter than C16 are fuel.

13.7.2.3 The integrator should establish a horizontal baseline under the output curve until the leading edge of C16 is reached. Establish a second baseline extending horizontally from the output curve, at the intersection of the output curve, and the leading edge of the C16 peak.

13.7.2.4 Column details are 10 ft by 0.125 in. (305 cm x 3.2 mm) SS; and the packing material is 5 % OV-1 on Chromosorb W HP.

13.7.2.5 Increase the oven temperature from 60 to 320°C, with the rate of change of temperature controlled at 8°C/min. Hold the temperature at 320°C for 16 min to elude oil.

13.7.3 Insolubles - Perform the following analysis on the used oil samples from Hours 108, 204, and 288: pentane insolubles. (See Test Method D893B, pentane only.)

13.7.4 Substitute Samples - Samples from hours 36, 132, and 228 can be substituted if the sample from the previous sampling period has been misplaced (see Fig.A7.9).

13.8 Other Deposits:
13.8.1 Piston Undercrown - Determine the deposit rating of the piston undercrown by comparison of the deposit on the rating location with CRC Induction System Rating Technique contained in CRC Manual No.16. Rate any areas where deposits have been altered by disassembly in accordance with deposits on the adjacent non-altered areas. Do not rate altered areas as clean. Identify the percentage of altered area on Fig.A7.1.5.

13.8.2 Ring Land Deposits - Determine the deposit rating of the ring land faces on all four pistons for each land type: crown land, second land (area between the two compression rings), and the oil ring land (area directly above the oil ring) by comparison of the deposit on the rating location with color chips contained in CRC Manual No.14 (non-rubbing scale, Appendix A.51). Average the results for each land type from each of the four pistons. Rate deposits that are less than 1.0 merits using two levels of carbon, heavy carbon, and light carbon. Heavy carbon is carbon that has more buildup when compared with adjacent surfaces and has a polished or rubbed finish. Assign a merit value of 0.0 to areas of heavy carbon. Rate all other deposits as light carbon and assign a merit value of 0.75 to those areas. Rate any areas where deposits have been altered by disassembly in accordance with deposits on the adjacent non-altered areas. Do not rate altered areas as clean. Identify the percentage of altered area on Fig.A7.1.5.