Artur Wolak

This study presents a comparative laboratory analysis of seven engine oil samples collected from passenger vehicles exhibiting significant viscosity deviations after operation. The aim was to demonstrate the diagnostic value of physicochemical testing in identifying mechanical or operational malfunctions that may not be detectable through routine vehicle servicing. Each oil sample was characterized by measurements of kinematic viscosity at 40 °C and 100 °C and Fourier-transform infrared (FTIR) spectra. The combination of these methods enabled the assessment of oxidation, fuel dilution, additive depletion, and contamination levels. The findings reveal consistent patterns linking abnormal viscosity reduction or increase with distinct spectral changes, particularly in the regions associated with oxidation (1710–1740 cm⁻¹), sulfation (1150–1250 cm⁻¹), and nitration (1600–1650 cm⁻¹). The study highlights that in cases of pronounced physicochemical anomalies, the use of alternative oil brands or viscosities cannot compensate for underlying mechanical issues. Laboratory diagnostics, combining viscosity testing and FTIR spectroscopy, provide an effective approach to pinpointing such faults, thus supporting preventive maintenance and informed decision-making in engine servicing. The proposed approach contributes to sustainability by enabling condition-based maintenance, reducing unnecessary oil replacement, and minimizing environmental impact associated with lubricant waste.

This study investigates fuel-induced oil dilution in hybrid powertrains using a combined assessment of kinematic viscosity and FTIR differential spectroscopy. Ten oil samples collected from hybrid vehicles operating under diverse real-world driving patterns were examined to determine how hybrid-specific operating conditions—such as frequent cold starts, extended start–stop phases and short, thermally unstable trips—influence lubricant ageing and, consequently, the energy efficiency of the combustion subsystem. In eight of the ten cases, a clear reduction in kinematic viscosity was observed, indicating the presence of volatile fuel fractions and confirming that fuel dilution is a dominant mechanism shaping the early stages of oil degradation in hybrid engines. FTIR analysis consistently revealed spectral shifts related to oxidation, nitration, sulfonation and additive depletion, together with hydrocarbon enrichment characteristic of fuel contamination. The co-occurrence of viscosity loss and FTIR band evolution demonstrates a strong and reproducible relationship between mechanical thinning of the lubricant and chemically driven transformation pathways, both of which can negatively affect frictional losses and energetic performance. Paper-based blot testing was used only as a supplementary qualitative tool and provided visual confirmation for samples exhibiting the strongest fuel-related FTIR signatures and viscosity changes. Although not mechanistically specific, the method reinforced the laboratory findings in cases of pronounced degradation. Overall, the results highlight the diagnostic value of combining viscosity data with FTIR spectral analysis to characterise fuel dilution and associated ageing mechanisms in hybrid combustion systems. This study contributes to a more comprehensive understanding of lubricant deterioration under real hybrid driving conditions and supports the development of practical monitoring strategies aimed at safeguarding both engine durability and the energy efficiency of hybrid powertrains.

This study explores the potential of paper chromatography for evaluating the condition of used engine oils. A set of 25 oil samples was collected from vehicles operated under real driving conditions and analyzed using both laboratory methods (FTIR spectroscopy, viscosity measurements) and commercial paper test kits. The aim was to quantitatively assess chromatographic spot parameters and investigate their relationships with physicochemical changes in the oil. Refined indicators based on diffusion and contamination zones were proposed and compared with parameters such as oxidation, sulfonation, nitration, and viscosity. The results showed mostly moderate correlations, with only partial consistency between chromatographic and laboratory-derived data. Nevertheless, the analysis highlights that paper chromatography may provide rapid and accessible additional insights for oil condition monitoring, although it cannot substitute standard laboratory testing.

Engine oil condition critically affects vehicle performance, fuel efficiency, and engine durability. While conventional oil change strategies are based on fixed intervals or mileage thresholds, they often neglect real operating conditions and the actual state of lubricant degradation. This study investigates nine used engine oil samples collected from passenger vehicles operating in diverse environments, including city traffic, highway routes, hybrid systems, and diesel engines. The oils were assessed using kinematic viscosity measurements and Fourier transform infrared (FTIR) spectroscopy to monitor key degradation indicators—oxidation, nitration, sulfonation, fuel dilution, soot contamination, and additive depletion. Each case is fully documented with detailed operational histories, facilitating a nuanced, real-world understanding of oil aging. The results demonstrate that degradation levels vary considerably, even under similar mileage ranges, highlighting the influence of urban usage patterns and engine design. In several cases, premature or delayed oil changes were observed, confirming that standard service intervals may be suboptimal. FTIR proved effective in detecting subtle chemical transformations, particularly in samples affected by biofuel components or prolonged thermal stress. These findings emphasize the value of integrating laboratory diagnostics into oil change decision-making and support more tailored maintenance strategies. Such an approach can reduce unnecessary oil replacement, limit waste generation, and extend engine lifespan, contributing to both environmental and economic sustainability. This study supports the implementation of condition-based oil change strategies to minimize lubricant waste and promote maintenance practices aligned with sustainability principles.

The increasing demand for the real-time monitoring of engine oil quality has driven the development of novel diagnostic methods. Traditional techniques primarily rely on physicochemical assessments, which, while effective, are often time consuming and require specialized laboratory equipment. This study explores the feasibility of using electrical property measurements to assess engine oil quality, offering a potential alternative for rapid, cost-effective diagnostics. A proprietary measurement system utilizing two innovative sensors—rectangular and concentric—was employed to evaluate the electrical characteristics of five commercially available synthetic engine oils. Key parameters, including impedance (|Z|), phase shift angle (θ), conductance (G), susceptance (B), parallel equivalent capacitance (Cp), and quality factor (Q), were measured across a frequency range of 100 Hz to 1.2 MHz. These results were correlated with conventional physicochemical parameters, specifically viscosity and infrared spectroscopy data, to determine the reliability and accuracy of electrical diagnostics in assessing oil degradation and quality variations. The findings indicate a correlation between selected electrical parameters and traditional laboratory measurements, particularly within the 1 kHz to 10 kHz frequency range, where the measurement repeatability was the highest. The study also identifies key challenges associated with sensor sensitivity to environmental factors and provides insights into optimizing the measurement process. The results contribute to the ongoing development of alternative, real-time oil condition monitoring techniques, potentially improving the reliability of automotive and industrial lubrication systems.

Reducing fuel consumption to decrease CO₂ emissions has become a key development factor in the automotive industry. An effective way to decrease fuel consumption is to reduce the influence of various sources of energy loss. One way to increase engine efficiency is to use low-viscosity engine oils to reduce friction losses in the engine’s tribological systems. The aim of the article was to analyze the relationship between the type of engine oil and fuel consumption in a group of 12 passenger cars. This was a homogenous group of identical cars, equipped with the same engine, operated under very similar conditions. Three groups of engine oils (Revline, Total, Orlen) were tested in vehicles and stressed with comparable workloads. The experiment was conducted over two years (two stages of research). The collected results were presented using graphs and compared using statistical tests, split into two stages of research, with four seasonal temperature groups. The study provides a detailed description of fuel consumption differences taking into account variations in ambient temperature. The analyses were focused on finding answers to two research questions: does the type of engine oil affect the variation in combustion levels, and what is the variability of fuel consumption in different seasons due to the ambient temperature variability? Briefly, in both stages of the study, vehicles using Revline oil attained the highest average fuel consumption throughout the study period. Vehicles using Total oil showed similar results to those using Revline oil, with the difference in fuel consumption not as noticeable during warmer months. Conversely, vehicles using Orlen oil demonstrated the lowest fuel consumption values during colder months, but higher levels during warmer months.

The paper presents the results of the analysis of selected physicochemical parameters of engine oils after their use. The oils were obtained both from urban buses belonging to the fleet of a municipal transport company in Lublin, Poland but also from the city of Pardubice in the Czech Republic. Five samples of 10W/40 semi-synthetic oil and four samples of 5W/30 synthetic oil were tested. Kinematic viscosity at 40°C and 100°C, oxidation, nitration, sulfonation, total acid number (TAN), total base number (TBN), remaining antiwear additives, water content, and glycol content, were assessed using infrared spectroscopy (FTIR). The tests were performed on the basis of the ASTM E2412-10 standard. The article also presents the exceedance of the limit values results for the selected parameters. The results of the research can be used in optimizing the engine oil change interval so that the decision to replace the oil is justified both in economic and technical terms, taking into account the need to maintain the service life of the bus.

The aim of this study was to assess whether electrical parameters (capacitance and conductivity) of fresh engine oils—tested over a wide range of measurement voltage frequencies—can be used for oil quality assessment and its identification, based on physicochemical properties. The study encompassed 41 commercial engine oils with different quality ratings (American Petroleum Institute (API) and European Automobile Manufacturers’ Association (ACEA)). As part of the study, the oils were tested for their total base number (TBN) and total acid number (TAN), as well as their electrical parameters, including impedance magnitude, phase shift angle, conductance, susceptance, capacitance and quality factor. Next, the results for all of the samples were examined for correlations between the mean electrical parameters and the test voltage frequency. A statistical analysis (k-means and agglomerative hierarchical clustering) was applied to group oils with similar readings, drawing on the values for all electrical parameters to produce group oils with the highest similarity to each other into clusters. The results show that the electrical-based diagnostics of fresh engine oils can serve as a highly selective method for identifying oil quality, offering much higher resolution than assessments based on the TBN or the TAN. This is further supported by the cluster analysis, with five clusters generated for electrical parameters of the oils, compared to only three generated for TAN- and TBN-based measurements. Out of all the tested electrical parameters, capacitance, impedance magnitude and quality factor were found to be the most promising for diagnostic purposes. The value of electrical parameters of fresh engine oils is mostly dependent on the test voltage frequency (with the exception of capacitance). The correlations identified in the course of the study can be used to select for those frequency ranges that offer the highest diagnostic utility.

Paper chromatography is a method that allows rapid assessment of the condition and identification of fuel, water and soot contaminants in engine oil. The paper contains an analysis of the suitability of rapid paper chromatography for assessing the operating quality of engine oil. It takes into account the comparison of physicochemical parameters by classical methods with the quality of commercial paper chromatography. The presented research allowed verifying the suitability of paper chromatography for laboratory evaluation of engine oil quality. It was found that a more extensive analysis of the oil condition is possible provided that the chromatographic separation time of oil dispensed onto filter paper is increased from 1 minute to 40 minutes. Linear relationships were observed between the surface area of the stain core after 40-minute separation and selected viscosity parameters (e.g. kinematic viscosity measured at 40° C). Based on rapid paper chromatography, it was found that reasonable decisions can be made about the quality of engine oil, and thus about replacement or further use of the oil.