NB/SH/T 0898-2015 Evaluation of low-temperature oil sludge performance of automotive engine oils Procedure VG method

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Card type: Test method

1. Method number / full name / English name / replacement relationship

• Standard number: NB/SH/T 0898—2015
• Chinese name: Evaluation of low-temperature oil sludge performance of automotive engine oils Procedure VG method
• English name: 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
• Replacement relationship: This standard is first published (original foreword: This standard is first published).
• Adoption relationship: Modified adoption by redrafting method of ASTM D6593-13a "Evaluation of deposit performance of gasoline engine oils using spark-ignition gasoline engines under low-temperature light-load conditions".
• Main technical differences from ASTM D6593-13a (original foreword):
  • Some referenced standards were modified to corresponding national standards and industry standards of our country.
  • Domestic test fuel was added, because the test requires a large amount of fuel, and long-term dependence on imports does not conform to national conditions.
  • Deleted the content in Chapter 11 regarding the introduction of TMC for calibration.
  • Deleted the relevant requirements for raters regarding TMC in Chapter 13, because our country's standards are not supervised by TMC.
  • Added an appendix for the test report format.
• Publication/implementation: published on 2015-10-27, implemented on 2016-03-01; issued by the National Energy Administration.
• Drafting unit: Sinopec Research Institute of Petroleum Processing.
• Main drafters: Lin Lei, Wang Shanshan, Li Shaoyu, Lu Wentong, Xing Jianqiang, Zhang Zhenhua, Yang Benfeng.
• Secretariat: National Technical Committee for Standardization of Petroleum Products and Lubricants, Subcommittee on Petroleum Fuels and Lubricants (SAC/SC1/TC280).
• Proposed by: China Petrochemical Corporation.

2. Scope of application and non-applicability

• Scope of application (Chapter 1): This standard specifies a test method for evaluating the tendency of gasoline engine oils to form deposits such as sludge and varnish. It is applicable to gasoline engine oils (for example: SL/GF-3, SM/GF-4, SN/GF-5) and automotive engine oils with relevant requirements.
• Method application (Chapter 5): This test method accelerates deposit formation through carefully selected test conditions to evaluate the anti-deposit formation performance of gasoline engine oils; this test method is correlated with actual service data. Together with other test methods, this test method defines the performance of SL/GF-3, SM/GF-4, SN/GF-5 grade gasoline engine oils. The engine used in this method is broadly representative of modern automobiles, but does not fully represent all engines; when extrapolating test results, this factor and the intensified operating conditions should be considered together.
• Non-applicability: no explicit "non-applicability" clause is provided in the available source.

3. Method principle

• Method summary (Chapter 4):
  • 4.1 Each test engine is assembled from many new parts, and all aspects of the assembly process are specified in detail.
  • 4.2 The test bench can control engine speed, load, air-fuel ratio and other operating parameters.
  • 4.3 The total test time is 216h. It includes 54 cycles, each cycle is 4h, and each cycle consists of 3 stages.
  • 4.4 The operating conditions are changed in each cycle, characterized by transitions among low-temperature, medium-temperature and low-load, and medium-load operating conditions.
  • 4.5 To accelerate deposit formation, the amount of blow-by entering the crankcase and the nitrogen oxide content in the blow-by are significantly increased. At the same time, fresh air in the crankcase is reduced, and the oil and coolant temperatures are lowered, causing water and fuel in the oil to condense.
  • 4.6 After the test ends, the performance of the test oil is evaluated by disassembling the engine and measuring the level of deposit formation.

4. Reagents and materials (purity / preparation)

• Solvent (7.7.1): No. 4 solvent oil conforming to GB 1922—2006 standard.
• Organic solvent (7.7.2): Penmul L460. Warning: flammable, health hazard.
• Engine cooling jacket flushing agent (7.7.3): Dearsol 134 acidic cleaning agent. Warning: flammable, health hazard.
• Cooling system cleaning agent (7.7.4): DuPont product or equivalent product. Warning: corrosive, health hazard.
• Test piece cleaning material (7.7.5): NAT-50, PDN-50 type soap agent. Warning: health hazard.
• Sealant (7.8.2): silicone-based sealant is used on the sealing parts of the rear seal shaft sleeve-cylinder block, cylinder block-cylinder head-front cover plate joint surface, cylinder head-front cover plate-rocker arm cover joint surface, and cylinder block-front cover plate-oil pan joint surface; silicone-based sealant will increase the silicon content in the engine oil after dissolution, so the amount used should be as small as possible.
• Gaskets and seals (7.8.3): new gaskets and seals must be used each time the engine is installed.
• Base oil: EF-411 type base oil (used for cylinder block/cylinder head spray-wash mixture 50V/50V, see 7.8.4.1, 7.9.4); EF-911 type base oil (used for coating cylinder walls, see 7.9.2).
• Test fuel (8.2.4): The test fuel used in Procedure VG is XC2721NX10 and TF2221LS20 and QS01-2009 or test fuel meeting the requirements of Table 3. Changing fuel or batch change requires calibration of the test bench. Note: XC2721NX10, TF2221LS20 are ASTM numbers; QS01-2009 is RIPP number.
• Test fuel specification range (Table 3): API gravity 58.7–61.2 (ASTM D1298 or ASTM D287); Reid vapor pressure 60.7–63.4 (GB/T 8017); sulfur content 0.01–0.04 (GB/T 17040); solvent-washed gum (mg/100mL) 22.2–35.0 (GB/T 8019); distillation range: initial boiling point 48.9–57.2, 10% recovery temperature 98.9–115.2, 50% recovery temperature 162.8–176.7, 90% recovery temperature 196.1–212.8 (GB/T 6536); appearance clean and bright; water content (volume fraction) ≤0.01 (GB/T 11133); lead content ≤10 (GB/T 8020); induction period ≥1440 (GB/T 8018).
• Typical data of test fuel QS01-2009 (Table 4): initial boiling point 35.2, 10% recovery temperature 62.6, 50% recovery temperature 113.0, 90% recovery temperature 170.6, final boiling point 198.1, residue (volume fraction) 1.2, loss (volume fraction) 2.3, sulfur content 9mg/kg, oxygen content (mass fraction) 0.11%, lead content 2.9mg/L, carbon content (mass fraction) 86.34%, hydrogen content (mass fraction) 13.52%, aromatic content (volume fraction) 29.7%, olefin content (volume fraction) 5.5%, induction period >1000min, copper strip corrosion (50℃) 1a, solvent-washed gum content 4.0mg/100mL, research octane number 95.
• Engine oil (8.3.1): each test requires at least 7.5L new oil; to prevent accidental loss, generally 20L new oil should be provided; oil samples should be ensured to be free of contamination.
• Coolant (8.4.1): engine coolant consists of deionized water (less than 0.34g/kg) or distilled water and commercial additive-containing ethylene glycol coolant concentrate in equal proportions. Rocker arm cover coolant consists of deionized water (less than 0.34g/kg) or distilled water and rust inhibitor, wherein 475mL rust inhibitor is added to every 15L deionized water or distilled water.

5. Instruments and equipment

• Test engine (6.1, 7.1): a four-stroke eight-cylinder 4.6LV type spark-ignition engine produced by Ford Motor Company, characterized by an overhead camshaft, swirl fast-burn cylinder head design, two valves per cylinder and intake port electronic fuel injection. Parts on the engine can be used for at most 4 tests; other components are see Appendix C; during the test, non-scoring parts may be replaced if oil-related problems are not involved.
• Test bench (6.2): a test bench suitable for the test engine is configured.
• Intake air supply equipment (6.3): intake air supply equipment meeting the requirements of the test control conditions is used to control the temperature, pressure and humidity of the engine intake air.
• Fuel supply system (6.4): an appropriate fuel supply system is used (see Figure 1).
• Control and data acquisition system (6.5): should meet the requirements in Appendix B.
• New parts required for each test (7.2): use the engine parts listed in Table D.1; all gaskets required for each engine assembly shall be new.
• Reusable parts (7.3): the crankshaft, connecting rod, timing chain cover plate and cylinder head can be used multiple times; the camshaft can be reused at most 4 times; Appendix D lists all reusable engine parts.
• Specially machined engine components (7.4): intake system components (Figure 2, Figure C.1, Figure C.2); camshaft baffle (Figure C.3); crankcase oil filler port (positions marked 8, 9 in Figure C.4); oil dipstick and oil dipstick tube (Figure C.6); oil pan (modified oil pan with baffle, Figure C.7); exhaust manifold (Figure C.15, Figure C.16, an exhaust oxygen sensor is installed after each exhaust manifold); flywheel (Appendix D); rocker arm cover (stainless steel material, designed with cooling water jacket and threads for fixing the camshaft baffle, Figure C.3~Figure C.5); oil filter (Figure C.8, filter screen specification 60μm); oil pan heat shield (fiberglass).
• Special engine measurement and installation tools (7.5): piston ring positioner (Figure C.9, place the piston ring inside the cylinder liner at a position 28.5mm from the upper edge of the cylinder liner); ring cutter; PCV valve flow measurement device (Figure C.10, accuracy should be able to reach 5%, resolution 0.05L/s, calibrated once every 6 months); engine repair tools (Appendix E); standard gauges (4 pieces: 90.345mm corresponds to 0.125mm piston, 90.470mm corresponds to 0.25mm piston, 90.595mm corresponds to 0.375mm piston, 90.700mm corresponds to 0.50mm piston); oil filter screen blow-off device; engine parts cleaning equipment (with spray, heating, and drying functions); cylinder honing machine (Sunnen CV-616 type); connecting rod heater (Sunnen CRH-50 type).
• Measurement devices (Chapter 9): temperature (9.1, 6 temperature points, thermocouple accuracy 0.5°, diameter 3mm length 100mm); pressure (9.2, 8 pressure measurement points); flow (9.3, Venturi flowmeter for engine coolant, orifice flowmeter for blow-by, 9.525mm orifice plate used in this test); fuel consumption (9.4, mass flowmeter, error should be within 1%); speed and load (9.5, dry dynamometer, fully closed-loop control system, drive inertia 0.8kg·m²±0.1kg·m²); exhaust (9.6, wide-range oxygen sensor, accuracy ±2%); humidity (9.7, hygrometer minimum dew point accuracy ±0.55℃ at 16℃).
• Other laboratory equipment (Chapter 10): STAR detector (diagnose EEC system faults and operational abnormalities); 5000mL beaker (add oil before test); 500mL beaker (top up oil).

6. Recommended operating conditions

• Formal test operating conditions (Table 2):
  • Stage 1: time 120min; engine speed 1200±5 r/min; engine power recorded; intake manifold absolute pressure 69±0.2 kPa; engine oil inlet temperature 68±0.5℃; engine coolant outlet temperature 57±0.5℃; engine coolant flow rate 48±2 L/min; engine coolant pressure (gauge pressure) 70±10 kPa; rocker cover coolant inlet temperature 29±0.5℃; rocker cover coolant flow rate 15±1 L/min; intake air temperature 30±0.5℃; intake air pressure (gauge pressure) 0.05±0.02 kPa; excess air factor (Lambda) 1.00±0.05; blow-by rate recorded; intake air humidity 11.4±0.8 g/kg; exhaust back pressure (gauge pressure) 104±2 kPa; fuel flow rate recorded.
  • Stage 2: time 75min; engine speed 2900±5 r/min; engine power recorded; intake manifold absolute pressure 66±0.2 kPa; engine oil inlet temperature 100±0.5℃; engine coolant outlet temperature 85±0.5℃; engine coolant flow rate recorded; engine coolant pressure (gauge pressure) 70±10 kPa; rocker cover coolant inlet temperature 85±0.5℃; rocker cover coolant flow rate 15±1 L/min; intake air temperature 30±0.5℃; intake air pressure (gauge pressure) 0.05±0.02 kPa; excess air factor (Lambda) 1.0±0.05; blow-by rate 60~70 L/min; intake air humidity 11.4±0.8 g/kg; exhaust back pressure (gauge pressure) 107±2 kPa; fuel flow rate recorded.
  • Stage 3: time 45min; engine speed 700±15 r/min; engine power 1.30±0.2 kW; intake manifold absolute pressure recorded; engine oil inlet temperature 45±1℃; engine coolant outlet temperature 45±1℃; engine coolant flow rate recorded; engine coolant pressure (gauge pressure) 70±10 kPa; rocker cover coolant inlet temperature 29±1℃; rocker cover coolant flow rate 15±1 L/min; intake air temperature 30±0.5℃; intake air pressure (gauge pressure) 0.05±0.02 kPa; excess air factor (Lambda) 0.75±0.03; blow-by rate recorded; intake air humidity 11.4±0.8 g/kg; exhaust back pressure (gauge pressure) recorded; fuel flow rate recorded.
• Intake air requirements (8.1): temperature 30±0.5℃, humidity 11.4g/kg±0.8g/kg, relative pressure 0.05kPa±0.02kPa. Air supply volume: the intake air supply system can provide 110L/s of compressed air.
• Fuel system control (8.2.2): keep the fuel temperature in the fuel rail below 50℃; the fuel rail pressure should be higher than 185kPa and remain stable.
• Fuel consumption (8.2.3): program VG requires approximately 3300L of fuel per test.
• Test stage transition conditions (Table 5):
  • Stage 3 to stage 1: engine speed reaches 1195 r/min within 5s–20s; intake manifold absolute pressure reaches 68.8kPa within 20s–80s; oil inlet temperature reaches 67.5℃ within 8min±2min; coolant outlet temperature reaches 56.5℃ within 6min±2min; rocker cover inlet temperature reaches 29℃ within 17min.
  • Stage 1 to stage 2: engine speed reaches 2895 r/min within 30s–90s; intake manifold absolute pressure reaches 66kPa±2kPa within 60s–150s; oil inlet temperature reaches 99.5℃ within 7min±2min; coolant outlet temperature reaches 84.5℃ within 7min±2min; rocker cover inlet temperature reaches 84.5℃ within 17min±2min.
  • Stage 2 to stage 3: engine speed reaches 715 r/min within 5s–20s; engine power reaches less than 3kW within 5s–20s; oil inlet temperature reaches 46℃ within 15min±2min; coolant outlet temperature reaches 46℃ within 9min±2min; rocker cover inlet temperature reaches 30℃ within 10min±2min; excess air factor (Lambda) is controlled within the range 0.705~0.765 within 15s.
• Break-in test conditions (Table 6): oil level measurement stage time greater than 2min; stage 1 5min, speed 1500±25 r/min, intake manifold absolute pressure recorded, oil inlet temperature 40℃, coolant outlet temperature recorded, rocker cover coolant inlet temperature recorded, excess air factor recorded, exhaust back pressure recorded; stage 2 15min, speed 2900±5 r/min, intake manifold absolute pressure 66±0.2 kPa, oil inlet temperature 100±0.2℃, coolant outlet temperature 85±0.5℃, rocker cover coolant inlet temperature 85±0.5℃, excess air factor 1.0, exhaust back pressure recorded; stage 3 45min, speed 700±15 r/min, power 1.30±0.2 kW, intake manifold absolute pressure recorded, oil inlet temperature 45±1℃, coolant outlet temperature 45±1℃, rocker cover coolant inlet temperature 29±1℃, excess air factor 0.75, exhaust back pressure recorded.
• Test bench calibration (Chapter 11): after the test bench has undergone 15 formal tests, calibrate the test bench with reference oil. If the results do not meet the calibration requirements, identify the cause and resolve it before performing reference oil calibration.

7. Sampling and specimen preparation

• Test oil (8.3.1): each test requires at least 7.5L of new oil; to prevent accidental loss, generally 20L of new oil should be provided; oil samples should be guaranteed free of contamination.
• Oil sample collection (12.3.4.1): perform oil top-up, oil level measurement, and sampling once every 24h.
  • a) within 10min before stage 3 of the test, drain 150mL of dead zone oil;
  • b) take 60mL analysis oil sample;
  • c) add back the dead zone oil;
  • d) after operating stage 3 for 10min, shut down the engine. Do not turn off the rocker cover coolant pump;
  • e) after the engine has been stopped for 20min±2min, measure and record the oil level height;
  • f) convert the level height value to g, the difference between the actual oil level height and the full scale is the oil consumption. Use the chart in Appendix I to determine the level height. At test 216h, no more oil is added, and the last drained oil is used as the oil sample for 216h;
  • g) if the oil level is lower than 400g below full scale, top up oil to 400g below full scale and record. Under no circumstances should the top-up amount exceed 400g below full scale;
  • h) if the oil level is higher than 200g above full scale, drain oil to 200g below full scale and record;
  • i) restart the engine after stopping for 30min±1min. After the engine has operated under the conditions of stage 3 for 5min±1min, it enters the formal test.
• Oil sample analysis (13.6.1): perform the following analysis on each 24h oil sample and the 216h oil sample: use methods GB/T 11137, GB/T 17476, NB/SH/T 0829 to analyze the oil samples for 40℃ kinematic viscosity, metal content, and fuel dilution, respectively.
• Specimen preparation: not provided in the available source as an independent "specimen preparation" chapter; the related preparation/pretreatment is distributed in Chapter 7 (parts preparation), Chapter 8 (fluids), Chapter 12 (test procedure).

8. Analysis procedure

• Pre-test preparation (12.1):
  • Engine break-in procedure (12.1.1): before the formal test, run the break-in test according to the conditions in Table 6.
  • Before the break-in test, add 3000g test oil to the engine. Operate the engine at a speed of 1500r/min±25r/min and an intake manifold vacuum of 37.6kPa until the oil temperature reaches 80℃±2℃ or the operating time exceeds 2min. After stopping for 20min±2min, determine and record the oil level height as shown in Appendix I. This level height is the full scale value for this test.
  • During the break-in test, check the operation of the EEC system, the blow-by level, the air-fuel ratio system leakage in stage 2 and stage 3, and allow air in the cooling system to escape.
  • In stage 1 of the break-in test, bleed all air from the engine and rocker cover cooling system, and check the system for leakage.
  • In stage 2 of the break-in test, measure the crankcase blow-by. Under normal conditions, during the break-in test the blow-by range is within 65L/min~75L/min. After 48h during the formal test, adjustment of piston ring end gap is not permitted.
  • In stage 3 of the break-in test, check the operation of the idle speed control system and the EEC system. When the oil temperature and coolant temperature reach 45℃±0.5℃, the excess air coefficient (Lambda) value should be close to the specified value in Table 6.
  • In stage 2 and stage 3, operate for 35min and record all parameter values respectively.
  • At the end of the break-in test, check and record the oil level height.
• Engine operating procedure (12.2):
  • Start the engine (12.2.1): turn on the ignition circuit, protection circuit, fuel system, fuel pump, and rocker cover coolant pump; connect the engine intake line; the engine should start within 4s.
  • Engine shutdown (12.2.2): normal shutdown procedure: a) adjust the engine speed to 700r/min±50r/min and hold for 10min; b) turn off the ignition; c) turn off the fuel pump; d) disconnect the intake pipe and reduce the intake pressure to atmospheric pressure. For abnormal shutdown procedure, follow 12.2.2.2.
  • Startup after abnormal shutdown (12.2.2.3): after starting the engine, operate in stage 3 condition for 5min, then return to the stage before shutdown.
  • Startup after the oil level measurement stage (12.2.2.4): after each oil level measurement, start the engine and operate for 5min; after the conditions meet the requirements of stage 3, enter the formal test procedure according to the transition conditions from stage 3 to stage 1 in Table 5.
  • General description of cyclic operation (12.2.3): the test consists of three stages; the three stages form one cycle; each cycle is 4h, with a total of 54 cycles 216h. For 6 consecutive cycles (24h), oil sampling and oil level adjustment are carried out.
  • Abnormal shutdown (12.2.4): the oil level check time of 30min is the normal shutdown time allowed by the method and has been counted in the test time.
• Periodic measurements and significance (12.3):
  • Blow-by measurement (12.3.1): in stage 2 of every 6 cycles, at 30min±5min, use the blow-by measuring instrument installed as shown in Figure 7 to measure and record the blow-by. During measurement, the engine should run smoothly, the blow-by temperature 32℃±?, and the temperature difference between the blow-by temperature and room temperature should not exceed ±5℃. For detailed measurement steps, see 12.3.1.1.
  • Ignition timing measurement (12.3.2): the ignition timing is set by EEC and can only be checked with the STAR detector.
  • Exhaust analysis (12.3.3): display the exhaust Lambda value in each stage of each cycle. When the engine oil and coolant temperatures reach a steady state, measure the exhaust Lambda value (approximately 20min±5min after entering each stage).
  • Adding oil and taking oil samples (12.3.4): every 24h, carry out oil addition, oil level measurement, and sampling once.
  • Daily maintenance (12.3.5): within the 30min of the normal shutdown for oil level measurement, simple maintenance of the engine and test bench may be carried out.
• Special maintenance procedures (12.4):
  • Blow-by adjustment (12.4.1): blow-by adjustment is only permitted during the break-in test and within the first 48h of the formal test. The blow-by will gradually decrease from the break-in test stage during the test, but within the first 120h of the test, the blow-by should remain between 60L/min~70L/min. Adjusting the blow-by is mainly achieved by changing the piston ring end gap or replacing the piston rings.
  • Adjustment for large blow-by (12.4.1.2): replace the compression rings with smaller end gaps to reduce blow-by.
  • Adjustment for small blow-by (12.4.1.3): increase the compression ring end gap to increase blow-by.
  • Engine disassembly and assembly during blow-by adjustment (12.4.2): engine disassembly and assembly should be carried out according to the procedures in 7.8 and 12.6.2 respectively.
• Key parameter checks (12.5): intake manifold vacuum, engine load, fuel consumption, knock, exhaust composition, crankcase pressure, oil pressure, oil inlet-outlet temperature difference, coolant inlet-outlet temperature difference.
• End of test (12.6):
  • Drain coolant and test oil (12.6.1): after completing the last cycle of the test, immediately drain all engine coolant and rocker cover coolant. To allow the test oil in the engine to flow completely back to the oil pan, the engine must stand on the test bench for 6h~12h before draining all test oil from the oil pan.
  • Engine disassembly (12.6.2): when disassembling the engine, special care should be taken not to damage deposits, and the parts corresponding to each cylinder should be marked.
  • Placement of parts (12.6.3): parts to be rated need to stand for 4h~8h so that the oil on them completely drains before rating. The rocker cover is placed vertically with the front end facing down; the camshaft baffle is placed vertically with the rear end facing down; the cylinder head is placed with the surface that contacts the cylinder head gasket facing down; the front cover plate is placed in the same orientation as when installed on the engine; the oil pan is placed with the surface that contacts the cylinder block facing down, at an angle of 45° to the ground, and with the oil pan downward; the oil pan baffle is placed vertically with the front end facing down; the oil screen is placed in the same orientation as when installed on the engine.
• Evaluation of test results (Chapter 13):
  • Rating room environment (13.1): ensure that the air in the rating room is clean and dust-free and that the room temperature is maintained within the range of 24℃±3℃. Except for the pistons, rocker cover, and cylinder block, all engine parts should be rated under cool white fluorescent lamps with an illuminance of 3800lx–5400lx (measured at 355mm from the tabletop) and a color temperature of 4100K. The pistons, rocker cover, and cylinder block are rated under fluorescent lamps with an illuminance of 3800lx–6500lx (measured at 355mm from the tabletop), against a white board facing away from 100%.
  • Sludge rating (13.2): perform sludge rating on the following parts: rocker cover (2 pieces), upper surface of cylinder head (2 pieces), camshaft baffle (2 pieces), timing chain cover plate, oil pan, and oil pan baffle. According to the provisions of SH/T 0510, rate the above test parts according to the requirements of Appendix K.
  • Varnish rating (13.3): perform varnish rating on the following parts: piston skirt (8 pieces, only the load-bearing surface is rated) and left and right camshaft baffles. After the sludge rating is completed, according to the provisions of SH/T 0510, rate the above test parts according to the requirements of Appendix K.
  • Plugging evaluation (13.4): oil screen plugging evaluation.
  • Evaluation of sticking (13.5): record the number of stuck rings. The definition and grades of stuck rings are given in Chapter 3. In the test report, list the number of cold-stuck rings and hot-stuck rings of the compression rings, as well as the sticking positions and the corresponding pistons.
  • Oil sample analysis (13.6): for each 24h oil sample and the 216h oil sample, perform analysis of 40℃ kinematic viscosity, metal content, and fuel dilution.
  • Additional measurements (13.7): measurement of intake and exhaust rocker arm pin wear for cylinder 8; piston ring end gap increment.

9. Qualitative and Quantitative and Calculation Formulas

• Blow-by correction formula (12.3.1.1): Q = V × [3.100P / (273.15 + T)]^1.5 Where: Q— corrected blow-by, L/min; V— blow-by, L/min; P— atmospheric pressure, kPa; T— blow-by temperature, ℃.
• Calculation formula for quality index QI (B.5.3): QI = 1 - (1/n) × Σ [ (U + L - 2X) / (U - L) ]² Where: X— measured parameter; U— allowable upper limit; L— allowable lower limit; n— number of measured parameters.
• Sludge rating (13.2.2): determine the sludge depth of each rating area according to the positions shown in the rating table. Each area is a circle with a diameter of 20mm. If sludge of different depths appears in a rating area, multiply the area percentage of each part by the volume coefficient of the different depth grades, add them, and look up the given value in Table 7 to obtain the sludge depth grade of that area. Convert the area percentage of each area multiplied by the corresponding sludge depth grade into a volume coefficient; add the volume coefficients to obtain the final volume coefficient, then convert it into the final sludge rating according to SH/T 0510.
• Oil screen plugging rate (13.4.1.3): take the natural logarithm of the sum of the oil sludge plugging result plus 1, that is, ln( oil screen plugging rate + 1); retain 4 decimal places in the calculation result, and report both the original value and the calculated value in the corresponding table. If the laboratory deviation is large, the result needs severity adjustment; retain 4 decimal places in the calculation result, then take the antilogarithm and subtract 1, convert back to the original numerical form, and record it as the final result in the corresponding table.
• Piston ring end gap increment (13.7.2): clean the top rings of pistons No. 1 to No. 8, place the piston rings into the standard cylinder liner used for measurement (7.5.5), and measure the end gap. Calculate the end gap increment, subtract the adjustments made during the test, calculate and record the average end gap increment of 8 piston rings, and determine and record the maximum end gap increment value.
• Fuel dilution amount (13.6.2): determine the fuel dilution amount of the oil sample.

10. Precision

• Precision and bias (Chapter 16): test the reliability of the test results (95% confidence level) according to the following provisions.
• Intermediate precision conditions (16.1.1): in the same laboratory, using the same test method, the operator, measuring equipment, test bench, test engine, and time may be changed to measure the same sample. Intermediate precision, relative to "repeatability" (repeatability is defined more strictly within laboratory conditions than intermediate precision), is more suitable for this test method.
• Intermediate precision limit i.p. (16.1.2): under intermediate precision conditions, the difference between two test results obtained from measuring the same sample must not exceed the value specified in Table 8.
• Reproducibility conditions (16.1.2.1): different operators, in different laboratories, using different equipment, according to the same test method, measure the same sample separately.
• Reproducibility limit R (16.1.2.2): under reproducibility conditions, the difference between two single, independent test results obtained from measuring the same sample must not exceed the value specified in Table 8.
• Reference oil statistical values (Table 8):
  • Average merit rating: S_p 0.45, i.p. 1.26, S_R 0.46, R 1.29.
  • Average varnish: S_p 0.25, i.p. 0.70, S_R 0.2, R 0.76.
  • Average sludge: S_p 0.10, i.p. 0.28, S_R 0.10, R 0.28.
  • Rocker cover sludge: S_p 0.819, i.p. 2.293, S_R 0.793, R 2.220.
  • Piston skirt varnish: S_p 0.20, i.p. 0.56, S_R 0.20, R 0.56.
  • Note: Some values source-text extraction in Table 8 are misaligned/duplicated, requires confirmation against the source standard (source-text extraction).
• Deviation (16.2): Using acceptable statistical methods to process reference oil test results can yield deviation; when significant deviation occurs, severity adjustment of non-reference oil test results is permitted.

11. Report

• Test report (Chapter 15): The test report format is given in Appendix L.
• Test report format (Appendix L, normative appendix): Procedure VG report format.
• The report content involves: test result evaluation (Chapter 13), test validity assessment (Chapter 14), oil sample analysis, blow-by flow rate, intake manifold absolute pressure, fuel consumption rate, oil consumption, engine part replacement, quality index, etc.
• Quality index report (B.5.7): Report the QI value in the report. If the final QI value of the reference oil test is less than 0.000, the test run process should be checked together with TMC.
• Dry sludge and foamy sludge deposits (13.2.2.3): If dry sludge and foamy sludge phenomena occur after the test, it is generally considered to be caused by poor engine lubrication over a long period. This phenomenon should be noted in the final test report, and the occurrence of this phenomenon and the area percentage should be recorded. Typically, dry sludge or bubbly sludge of approximately 6% area will appear on the rocker cover (left or right).
• Adhesion evaluation report (13.5.1): List in the test report the number of cold-stuck and hot-stuck compression rings, as well as the location of sticking and the corresponding piston.
• Oil screen clogging report (13.4.1.3): Report both the original values and the calculated values in the corresponding table.

12. Normative References

• GB 1922—2006 Solvent naphtha for paints and cleaning
• GB/T 5096 Petroleum products—Determination of copper corrosion
• GB/T 5487 Determination of gasoline octane number (research method)
• GB/T 6536 Determination of distillation characteristics of petroleum products at atmospheric pressure
• GB/T 8017 Determination of vapor pressure of petroleum products—Reid method
• GB/T 8018 Determination of oxidation stability of gasoline (induction period method)
• GB/T 8019 Determination of gum content in fuels—Jet evaporation method
• GB/T 8020 Determination of lead content in gasoline (atomic absorption spectrometry)
• GB/T 11132 Determination of hydrocarbon types in liquid petroleum products—Fluorescent indicator adsorption method
• GB/T 11133 Determination of water content in liquid petroleum products (Karl Fischer method)
• GB/T 11137 Determination of kinematic viscosity of dark petroleum products (reverse flow method) and calculation of dynamic viscosity
• GB/T 13377 Crude petroleum and liquid or solid petroleum products—Determination of density or relative density—Capillary-stoppered pyknometer and graduated bicapillary pyknometer methods
• GB/T 17040 Determination of sulfur content in petroleum and petroleum products—Energy-dispersive X-ray fluorescence spectrometry
• GB/T 17476—1998 Determination of additive elements, wear metals, and contaminants in used lubricating oils and certain elements in base oils (inductively coupled plasma atomic emission spectrometry)
• GB/T 17754—2012 Tribology terminology
• NB/SH/T 0474 Determination of diluted gasoline content in in-service gasoline engine oils—Gas chromatography
• SH/T 0510 Rating method for gasoline engine engine tests
• SH/T 0656 Determination of carbon, hydrogen, and nitrogen in petroleum products and lubricants (elemental analyzer method)
• SH/T 0663 Determination of certain alcohols and ethers in gasoline (gas chromatography)
• NB/SH/T 0829 Boiling range 174℃~700℃ Determination of boiling range distribution of petroleum fractions—Gas chromatography
• ASTM D 235 Specification for Mineral Spirits (Petroleum Spirits) (Hydrocarbon Dry Cleaning Solvent) (solvent gasoline specification)
• ASTM D 287 Test Method for API Gravity of Crude Petroleum and Petroleum Products (Hydrometer Method) (crude petroleum and petroleum products API