A method for verifying the dilution of diesel engine oil

Abstract

This invention discloses a method for verifying diesel engine oil dilution, relating to the field of engine testing. The invention includes: S1, test preparation; S2, constructing and executing an enhanced test cycle, specifically, actively triggering a high-dilution-risk operating condition module during the high-risk phase of the WHTC cycle. This module is activated when the coolant temperature and torque change rate meet specific boundary conditions, and during this period, it collaboratively executes extreme after-injection strategies and proactive thermal management interventions to accelerate risk exposure; S3, simultaneously monitoring process data such as the concentration of unburned hydrocarbons in the crankcase ventilation; S4, weighing and calculating the oil dilution rate after the test; S5, performing event correlation, phased comparison, and multi-dimensional analysis based on process data to achieve precise typological diagnosis of the root cause of dilution; S6, modifying the calibration by calling targeted suggestions from the optimization decision rule base according to the diagnostic type, and performing closed-loop verification. This invention achieves rapid exposure, precise location, and efficient optimization of oil dilution problems.

Description

Technical Field

[0001] This invention relates to the field of engine testing, and more specifically, to a method for verifying the dilution of diesel engine oil. Background Technology

[0002] With increasingly stringent global emission regulations, advanced technologies such as high-pressure common rail, direct injection, and diesel particulate filters are widely used in diesel engines. While improving fuel economy and reducing emissions, these technologies also bring significant risks related to fuel dilution of engine oil. Particularly during the active regeneration of the diesel fuel filter (DPF), methods such as after-injection are needed to increase exhaust temperature to burn off particulate matter. Under conditions such as cold starts and short-distance driving, unburned fuel is more likely to seep through the cylinder walls into the crankcase and mix with the engine oil. When engine oil is diluted by fuel, its viscosity, lubrication properties, and cleaning and dispersing abilities decrease sharply, leading to accelerated engine wear. In severe cases, this can cause fatal malfunctions such as cylinder scoring and bearing damage, and also affect the normal operation of the aftertreatment system. Therefore, effective assessment and control of engine oil dilution risks during the engine development stage is crucial.

[0003] Currently, the industry primarily relies on two methods for verifying engine oil dilution. The first method involves periodically sampling and sending samples to a laboratory for testing during routine durability and reliability tests (such as rated power durability and thermal shock tests). This method has significant drawbacks: its operating conditions differ greatly from the complex transient conditions of real vehicles, leading to a severe deviation between the test boundary conditions (fuel injection quantity, temperature, load change rate) and actual market conditions. The verification results often fail to accurately reflect the real risks faced by the product in actual use, potentially resulting in potentially defective products entering the market.

[0004] The second type of method attempts to improve upon the above shortcomings, for example by collecting the load spectrum of the vehicle during actual operation and reproducing that load spectrum on a test bench. This method enhances the realism of the operating condition simulation, but it is essentially still a passive, long-term comprehensive durability test. To observe statistically significant oil dilution, hundreds of hours of operation are typically required, resulting in high development cycles and costs. More importantly, this method can only provide the final result of whether or not the limits are exceeded; it cannot capture the specific transient events of dilution during the test in real time, nor can it distinguish whether the dilution is mainly caused by cold start, load transients, or regeneration strategies. When a problem is discovered, engineers can only perform general optimization control strategies, lacking precise improvement directions, making the troubleshooting and optimization process inefficient and trapped in a trial-and-error cycle. Summary of the Invention

[0005] The purpose of this invention is to provide a diesel engine oil dilution verification method, which can quickly and proactively expose oil dilution risks, accurately locate the root cause of the problem, and guide efficient optimization in testing and development, thereby shortening the R&D cycle, reducing development costs, and fundamentally improving product reliability and market adaptability.

[0006] To achieve the above objectives, the present invention employs the following technical means: A method for verifying the dilution of diesel engine oil includes the following steps: S1. Engine performance verification and test preparation: Confirm that the engine under test meets the performance requirements, replace the engine oil and oil filter, and record the initial total mass of the engine oil. M_initial And extract initial engine oil samples; S2. Construct and execute an enhanced test cycle. On an engine bench, run an improved WHTC. In the preset high-risk phase of the cycle, actively trigger and execute a high-dilution-risk operating condition module. When the high-dilution-risk operating condition module is triggered, coordinately control the engine to enter a set boundary operating state that is prone to causing fuel dilution. S3. Synchronous monitoring and recording of process data: During the execution of step S2, engine operating parameters, activation event markers of the high dilution risk condition module, and real-time data on the concentration of unburned hydrocarbons in the crankcase ventilation pipeline are collected and recorded synchronously. S4. Post-test analysis and oil dilution rate calculation: After completing the set enhanced test cycle, drain and weigh the total mass of the oil after the test. M_final And calculate the oil dilution rate D according to the formula: ; S5. Process diagnosis and root cause localization: Based on the process data recorded in step S3, perform time-domain correlation analysis on the transient peak concentration of unburned hydrocarbons in the crankcase ventilation pipeline and the activation event of the high dilution risk mode module, and compare the peak response of unburned hydrocarbons and the oil increment rate of the same risk event in different test stages to locate the root cause type of the excessive oil dilution rate. S6. Generate precise optimization suggestions and perform closed-loop verification. Based on the root cause location results of step S5, retrieve targeted engine control parameter optimization suggestions from the preset optimization decision rule base, modify the engine control unit calibration data, and repeat steps S2 to S4 for verification until the oil dilution rate meets the predetermined threshold.

[0007] Preferably, the definition and triggering of the high dilution risk operating condition module in step S2 satisfy the following conditions: The module is triggered when the engine operating state simultaneously meets the following two boundary conditions: A. The coolant temperature is below the set threshold; B. The positive rate of change of engine torque demand is higher than the set threshold; During module activation, the engine's conventional control strategy is overridden, and a set of predetermined control parameters that are prone to causing fuel wetting are enforced.

[0008] Furthermore, the improved WHTC refers to actively controlling the engine's operating state to meet the triggering conditions by identifying one or more phase points that satisfy the module triggering conditions in the basic WHTC cycle through a host computer test program, thereby forcibly activating the high dilution risk operating condition module at the phase point.

[0009] Furthermore, the control parameters forcibly executed during the activation of the high dilution risk operating condition module include at least the post-injection quantity and post-injection timing, the values ​​of which are set to extreme or boundary values ​​within the calibrated allowable range, for pressure testing of the fuel system.

[0010] Furthermore, in step S2, during the activation of the high dilution risk operating condition module, the coordinated control also includes active intervention in the engine thermal management system, specifically, temporarily restricting or shutting down the large coolant circulation and reducing or shutting down the cooling fan speed to slow down the rate of temperature rise of the engine block during the high-risk phase.

[0011] Furthermore, in step S2, during the activation of the high dilution risk operating condition module, multiple different combinations of post-injection strategies are systematically tested. Each combination includes different post-injection amounts, post-injection timings, and post-injection frequency. By comparing the peak concentration of unburned hydrocarbons in the crankcase ventilation pipe and the oil increment rate caused by different strategy combinations, the contribution of each injection parameter to the oil dilution risk is quantified.

[0012] Furthermore, the process data monitored in step S3 also includes the real-time change curve of the engine oil temperature; in step S5, the cumulative time during which the engine oil temperature is below the critical fuel evaporation temperature threshold is calculated throughout the entire test process, and the correlation between the cumulative time and the final engine oil dilution rate D is analyzed to evaluate the contribution of the thermal management strategy to the dilution risk.

[0013] Furthermore, in step S3, the concentration of unburned hydrocarbons is monitored in real time at a frequency of not less than 1 Hz using an online Fourier transform infrared spectrometer or flame ionization detector installed on the crankcase ventilation duct; the unburned hydrocarbon concentration data, engine operating parameters, and module activation event markers are synchronized using a unified timescale.

[0014] Furthermore, the comparison of different test stages in step S5 specifically involves dividing the entire enhanced test process into at least two consecutive stages, calculating the average oil increment per unit time or per unit cycle number in each stage, and comparing the peak height of unburned hydrocarbons in the crankcase ventilation duct associated with the same high dilution risk operating condition module setting when triggered in different stages to determine whether the dilution trend is approaching saturation, continuing, or changing.

[0015] Furthermore, the preset optimization decision rule base mentioned in step S6 contains a list of optimization suggestions mapped according to the root cause type; If the root cause is identified as being primarily due to cold operating conditions, optimization suggestions include increasing idle speed, modifying the target value for coolant temperature in the low-temperature zone, or prohibiting post-spraying under low-temperature conditions. If the root cause is identified as being dominated by transient load changes, optimization suggestions include optimizing the transient coordinated control of boost pressure and exhaust gas recirculation, or introducing fuel injection quantity correction based on torque change rate. If the root cause is identified as a regeneration strategy-driven issue, optimization suggestions include recalibrating the relationship between fuel injection quantity and exhaust temperature, or optimizing the injection timing. If the root cause is identified as being driven by thermal management strategies, optimization recommendations include calibrating more aggressive cooling fan control logic or increasing the thermostat opening temperature threshold.

[0016] The present invention has the following beneficial effects during use: By proactively constructing and repeatedly applying high-risk boundary condition modules, it is possible to simulate and accumulate diluted risk intensity equivalent to that encountered over thousands of kilometers in actual use within tens of hours, reducing the verification cycle by more than an order of magnitude from the traditional hundreds of hours and accelerating the R&D process.

[0017] Achieve precise risk exposure and root cause diagnosis. Through proactive experimental design that defines risk events / programmed implantation and online process monitoring, it is possible to strongly correlate macroscopic oil dilution results with microscopic, specific engine control events, thereby accurately pinpointing the root cause of the problem rather than just providing a general conclusion.

[0018] Targeted optimization suggestions generated based on diagnostic results transform calibration engineers' optimization work from blind trial and error to targeted efforts. Combined with a rapid closed-loop verification process, it enables systematic optimization of control strategies, significantly improving calibration quality and development efficiency, fundamentally reducing product market risk, and enhancing reliability. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0020] Therefore, the following detailed description of embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other.

[0022] A method for verifying the dilution of diesel engine oil, characterized by comprising the following steps: S1. Engine Performance Validation and Test Preparation Specifically, this includes confirming that the basic performance of the engine under test meets the requirements, then replacing the engine oil and oil filter, accurately weighing and recording the initial total mass of the engine oil. M_initial And extract initial engine oil samples.

[0023] S2. Construct and execute the reinforcement test loop. Its core is to proactively design and run a reinforcement test loop: First, a high-dilution-risk operating condition module is defined, triggered when the engine coolant temperature is below a set threshold and the positive rate of change of engine torque demand is above a set threshold. During module activation, a set of preset boundary control parameters that are prone to causing fuel wetting are forcibly executed.

[0024] Secondly, the WHTC is modified programmatically. Through the host computer program, high-risk phases identified in the basic WHTC cycle are actively controlled to meet the aforementioned triggering conditions, thereby forcibly activating the risk module and realizing the programmatic implantation and synchronization of risk events.

[0025] During module activation, multivariate collaborative boundary exploration is performed: a. Conduct stress tests on the fuel injection strategy and systematically apply multiple sets of boundary post-injection strategy combinations (such as maximum post-injection quantity, latest post-injection timing, etc.).

[0026] b. Actively intervene in the thermal management system, temporarily restrict the large circulation of coolant and reduce the fan speed to deliberately delay the rise in cylinder block temperature.

[0027] c. Continuously monitor the engine oil temperature history, including the cumulative time the engine oil temperature remains below the critical fuel evaporation temperature threshold.

[0028] S3. Synchronous monitoring and recording of process data Throughout the test, the concentration of unburned hydrocarbons in the crankcase ventilation system was monitored in real time at a high frequency of ≥1Hz using an online Fourier transform infrared spectrometer or flame ionization detector. Simultaneously, all engine operating parameters, oil temperature, and activation event markers for high-risk operating condition modules were collected, and all data were aligned using a unified timescale.

[0029] S4. Post-test analysis and calculation of engine oil dilution ratio After completing the set reinforcement test cycle, drain the engine oil and weigh the parts to obtain the total mass. M_final According to the formula, the oil dilution rate D is calculated as follows: ; S5. Process Diagnosis and Root Cause Analysis In-depth analysis based on the process data recorded in step S3: Event correlation analysis was performed to correlate the transient peak concentration of unburned hydrocarbons in the crankcase ventilation duct with the activation event of the high-risk operating condition module in the time domain, thereby identifying specific risk events.

[0030] A phased comparative analysis was conducted, dividing the test into continuous phases. The peak response of unburned hydrocarbons and the rate of oil volume increase were compared at different stages of the same risk event to determine the dilution trend.

[0031] By combining multi-dimensional data such as cumulative low temperature time, the root cause of excessive dilution can be diagnosed, such as cold-condition-dominated type (Type A), transient load-dominated type (Type B), regeneration strategy-dominated type (Type C), or thermal management-dominated type (Type D).

[0032] S6. Generate precise optimization suggestions and perform closed-loop verification. Based on the diagnostic type in step S5, targeted optimization suggestions are output from the preset optimization decision rule base (e.g., optimizing cold start calibration for type A, and optimizing post-injection strategy for type C). After modifying the engine control unit calibration data according to the suggestions, steps S2 to S4 are re-executed for verification, forming a rapid development closed loop until the oil dilution ratio meets the requirements.

[0033] The following will provide a detailed explanation through specific examples.

[0034] Rapid assessment and optimization of oil dilution risk for a 6-cylinder high-pressure common rail diesel engine that meets China VI emission standards: 1. Test preparation and performance verification First, mount the engine under test on an engine dynamometer rig with high dynamic response capability and connect all necessary sensors and data acquisition systems. Follow the steps in S1 as follows: Basic performance sweep tests were conducted on the engine to confirm that its key parameters such as external characteristics, torque, power, and fuel consumption are consistent with the development goals.

[0035] After the engine has warmed up (oil temperature > 90°C), stop it. Open the bleed screw to drain the old oil and remove the old oil filter.

[0036] Weigh a new, compliant oil filter, record its weight, and install it onto the engine.

[0037] Using a high-precision oil dispenser, add the specified type and grade of new engine oil into the engine until it reaches the mark on the dipstick, and record the total mass of the oil added.

[0038] After starting the engine and idling for 3 minutes, stop the engine and let it stand for 3 minutes. Check again and ensure that the oil level is accurately at the middle mark. Then, take a 200g oil sample from the dipstick sleeve, seal it and mark it as "0h reference sample".

[0039] Calculate the initial total oil mass: The initial oil volume is the mass of added oil minus the initial sample mass.

[0040] 2. Constructing and executing reinforcement test loops The core is to programmatically run a reinforced WHTC loop.

[0041] Define a high-dilution-risk operating condition module: The module trigger conditions are defined as coolant temperature < 60℃ and torque change rate > 80Nm / s. After the module is activated, the following are enforced: the post-injection quantity is 95% of the maximum value allowed by calibration, and the post-injection timing is delayed to 20° crankshaft rotation before the exhaust valve opens.

[0042] Programmed Implantation: Analysis of the standard WHTC cycle. Two high-risk phases were identified: (1) 120 seconds after the start of cold start (the first rapid load acceleration); (2) a high-load ramp point in the middle of the cycle. Using a host computer test program (such as ETASICA or NILabVIEW), at these two time points, the dynamometer and ECU were coordinated to ensure that the engine state precisely matched the above triggering conditions, thereby forcibly activating the risk module. Each module lasted for 10 seconds. In this way, a standard 1800-second WHTC cycle was transformed into an enhanced cycle containing two active risk injections.

[0043] Multivariate collaborative boundary exploration: Thermal management intervention: Write logic in the host computer program to send a temporary overwrite command to the ECU every time the risk module activation signal is issued, forcibly set the cooling fan duty cycle to 0%, and set the electronic thermostat target opening to the minimum, for 12 seconds (overwrite module duration).

[0044] Injection strategy stress test: During the first activation, the combination of the maximum post-injection quantity and the latest timing mentioned above is applied. During the second activation, the combination of the staged post-injection quantity (85% of the maximum value) and the same latest timing is applied to compare the effects of different fuel quantities.

[0045] Oil temperature monitoring: Records the oil temperature in the oil pan throughout the process and sets the critical temperature threshold for fuel evaporation to 80℃.

[0046] 3. Synchronous monitoring of process data An online Fourier transform infrared (FTIR) gas analyzer is installed on the crankcase ventilation duct outlet line to monitor the total hydrocarbon (THC) concentration in real time, with a sampling frequency of 2Hz. Through a data acquisition system, the FTIR THC signal, ECU engine operating data (speed, torque, coolant temperature, post-injection fuel quantity, etc.), module activation event marker signals from the host computer, and oil temperature signals are all synchronized and recorded using the same GPS timing module.

[0047] 4. Execution Testing and Final Analysis With the engine locked in a combination of normal and regeneration modes, run the enhanced WHTC cycles described above for 20 consecutive cycles. After every 5 cycles, briefly stop the engine and check the oil level. If the level is below the lower mark, add oil to the middle mark and record the amount added.

[0048] After completing 20 cycles, proceed to step S4: After warming up the engine, drain all the engine oil and weigh it to obtain the mass of the drained oil; remove the oil filter and weigh it to obtain the mass of the used oil filter. Calculate the final total mass of engine oil: Total mass = Mass of drained engine oil plus mass of used oil filter - Mass of new oil filter.

[0049] Calculate the current oil dilution rate using the formula.

[0050] 5. Process Diagnosis and Root Cause Analysis Event Correlation Analysis: Process Data. It was found that approximately 1.5 seconds after the first risk event (acceleration after cold start) was triggered in cycles 1, 6, 11, and 16, the THC concentration in the crankcase ventilation duct experienced a spike from ~200 ppm to >1200 ppm. However, after the second risk event (hot load transient), the THC peak was only ~500 ppm. This directly demonstrates that coolant temperature conditions have a decisive influence on the occurrence of dilution.

[0051] Phased Comparison: The 20 cycles were divided into cycles 1-10 (Phase I) and cycles 11-20 (Phase II). Analysis revealed that in Phase I, the average THC peak caused by the same cold start risk event was 1350 ppm, while in Phase II it decreased to 1100 ppm. However, the rate of oil volume increase did not decrease proportionally in Phase II. Combined with oil temperature data, it was found that the average oil temperature in Phase II was 15°C higher than in Phase I, but the cumulative time below the fuel volatilization critical temperature threshold remained quite long.

[0052] Diagnostic Conclusion: Based on the above, the problem is diagnosed as a hybrid of Type A (dominated by cold operating conditions) and Type D (dominated by thermal management). The core issue is that the engine warms up too slowly in the early test cycles, leading to a persistent cold wall effect. Even in subsequent cycles, although the overall oil temperature rises, the cylinder wall temperature may still be insufficient during the risky transients.

[0053] 6. Closed-loop optimization and verification Optimization suggestions are generated: Based on the diagnostic conclusions, suggestions are retrieved from the rule base: 1) Optimize the coolant thermal management MAP to increase the target water temperature under low speed and low load; 2) When the coolant temperature is below 60°C, DPF active regeneration is prohibited (i.e., post-spraying is prohibited).

[0054] Implementation and Verification: The engineer modifies the ECU calibration data according to the recommendations. The optimized ECU is then reinstalled in the same engine, and steps 2-5 are repeated using the exact same enhanced test cycle program, the same risk module settings, and the same total of 20 cycles.

[0055] Results Comparison: After optimization, the THC peak triggered by cold start risk events decreased from >1200ppm to below 600ppm. Oil temperature rise accelerated, and the cumulative time below the fuel evaporation critical temperature threshold was shortened by 40%. The final calculated oil dilution rate was significantly lower than the oil dilution rate before optimization and also below the target threshold. This completes a full rapid development loop.

[0056] For the solution in this embodiment, most existing technologies focus on improving the simulation of working conditions more realistically. This embodiment shifts from a holistic approach to a reverse approach: actively defining, programmatically generating, and intensively repeating the most dangerous working condition segments, combining stress testing with fault injection. High-risk working condition modules are implanted as programmable objects into the standard loop.

[0057] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for verifying the dilution of diesel engine oil, characterized in that, Includes the following steps: S1. Engine performance verification and test preparation: Confirm that the engine under test meets the performance requirements, replace the engine oil and oil filter, and record the initial total mass of the engine oil. M_initial And extract initial engine oil samples; S2. Construct and execute an enhanced test cycle, run the improved WHTC on the engine bench, and actively trigger and execute the high-dilution-risk operating condition module in the preset high-risk phase of the cycle; When the high-dilution-risk operating condition module is triggered, the engine is controlled to enter a pre-defined boundary operating state that is prone to causing fuel dilution. S3. Synchronous monitoring and recording of process data: During the execution of step S2, engine operating parameters, activation event markers of the high dilution risk condition module, and real-time data on the concentration of unburned hydrocarbons in the crankcase ventilation pipeline are collected and recorded synchronously. S4. Post-test analysis and oil dilution rate calculation: After completing the set enhanced test cycle, drain and weigh the total mass of the oil after the test. M_final And calculate the oil dilution rate D according to the formula: ； S5. Process diagnosis and root cause localization: Based on the process data recorded in step S3, perform time-domain correlation analysis on the transient peak concentration of unburned hydrocarbons in the crankcase ventilation pipeline and the activation event of the high dilution risk mode module, and compare the peak response of unburned hydrocarbons and the oil increment rate of the same risk event in different test stages to locate the root cause type of the excessive oil dilution rate. S6. Generate precise optimization suggestions and perform closed-loop verification. Based on the root cause location results of step S5, retrieve targeted engine control parameter optimization suggestions from the preset optimization decision rule base, modify the engine control unit calibration data, and repeat steps S2 to S4 for verification until the oil dilution rate meets the predetermined threshold.

2. The diesel engine oil dilution verification method according to claim 1, characterized in that, The definition and triggering of the high dilution risk operating condition module in step S2 meet the following conditions: The module is triggered when the engine operating state simultaneously meets the following two boundary conditions: A. The coolant temperature is below the set threshold; B. The positive rate of change of engine torque demand is higher than the set threshold; During module activation, the engine's conventional control strategy is overridden, and a set of predetermined control parameters that are prone to causing fuel wetting are enforced.

3. The diesel engine oil dilution verification method according to claim 2, characterized in that, The improved WHTC refers to the active control of the engine's operating state to meet the triggering conditions by identifying one or more phase points that satisfy the module triggering conditions in the basic WHTC cycle through a host computer test program, thereby forcibly activating the high dilution risk operating condition module at the phase point.

4. The diesel engine oil dilution verification method according to claim 2, characterized in that, The control parameters that are forcibly executed during the activation of the high dilution risk operating condition module include at least the post-injection quantity and post-injection timing, and their values ​​are set to extreme or boundary values ​​within the calibrated allowable range for pressure testing of the fuel system.

5. A diesel engine oil dilution verification method according to claim 1 or 2, characterized in that, In step S2, during the activation of the high dilution risk operating condition module, the coordinated control also includes active intervention in the engine thermal management system, specifically, temporarily restricting or shutting down the large coolant circulation and reducing or shutting down the cooling fan speed to slow down the rate of temperature rise of the engine block during the high-risk phase.

6. The diesel engine oil dilution verification method according to claim 1, characterized in that, In step S2, during the activation of the high dilution risk operating condition module, multiple different combinations of post-injection strategies are systematically tested. Each combination includes different post-injection amounts, post-injection timings, and post-injection frequency. By comparing the peak concentration of unburned hydrocarbons in the crankcase ventilation pipe and the oil increment rate caused by different strategy combinations, the contribution of each injection parameter to the oil dilution risk is quantified.

7. The diesel engine oil dilution verification method according to claim 1, characterized in that, The process data monitored in step S3 also includes the real-time change curve of the engine oil temperature; in step S5, the cumulative time during which the engine oil temperature is below the critical temperature threshold for fuel volatilization is calculated throughout the entire test process, and the correlation between the cumulative time and the final engine oil dilution rate D is analyzed to evaluate the contribution of the thermal management strategy to the dilution risk.

8. The diesel engine oil dilution verification method according to claim 1, characterized in that, In step S3, the concentration of unburned hydrocarbons is monitored in real time at a frequency of not less than 1 Hz using an online Fourier transform infrared spectrometer or flame ionization detector installed on the crankcase ventilation duct; the unburned hydrocarbon concentration data, engine operating parameters, and module activation event markers are synchronized using a unified time scale.

9. The diesel engine oil dilution verification method according to claim 1, characterized in that, The comparison of different test stages in step S5 specifically involves dividing the entire enhanced test process into at least two consecutive stages, calculating the average oil increment per unit time or per unit cycle number in each stage, and comparing the peak height of unburned hydrocarbons in the crankcase ventilation duct associated with the same high dilution risk operating condition module setting when triggered in different stages to determine whether the dilution trend is approaching saturation, continuing, or changing.

10. The diesel engine oil dilution verification method according to claim 1, characterized in that, The preset optimization decision rule base mentioned in step S6 contains a list of optimization suggestions mapped according to the root cause type; If the root cause is identified as being primarily due to cold operating conditions, optimization suggestions include increasing idle speed, modifying the target value for coolant temperature in the low-temperature zone, or prohibiting post-spraying under low-temperature conditions. If the root cause is identified as being dominated by transient load changes, optimization suggestions include optimizing the transient coordinated control of boost pressure and exhaust gas recirculation, or introducing fuel injection quantity correction based on torque change rate. If the root cause is identified as a regeneration strategy-driven issue, optimization suggestions include recalibrating the relationship between fuel injection quantity and exhaust temperature, or optimizing the injection timing. If the root cause is identified as being driven by thermal management strategies, optimization recommendations include calibrating more aggressive cooling fan control logic or increasing the thermostat opening temperature threshold.

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