Lubricating Oil Research Articles

STUDY ON THE DEVELOPMENT OF THE WOODEN HYBRID STRUCTURAL SYSTEM WITH LAG-SCREW BOLTS

Recently, governments of developed countries, such as Japan and other European and North America countries, have encouraged using forest resources to reduce carbon dioxide (CO2) emissions. Cross-laminated timber (CLT) is a solid wood panel commonly used as a structural material to construct moderate-to-large-sized buildings because of its high strength and stiffness. Hence, we proposed replacing reinforced concrete slabs with CLT floor panels in moderate-to-large-sized buildings. The push-out shear test was conducted to investigate the shear performance of the proposed connection method between steel beams and CLT panels. The experimental variables denote the fiber direction of a CLT panel concerning test loading and lubricant oil used for fastening hexagon head bolts. A testing machine was used to apply shear load in a vertical direction using a pressure plate and rotational pins. Based on the results, the lubricated specimens exhibited greater initial stiffness than the unlubricated specimens. In addition, lubricant oil facilitated the practical application of tensile forces to hexagon head bolts. European Yield Theory was used to evaluate the yield shear strength of each connection method.

Microbiological Status, Physico-chemistry and Plant Performance in Spent Lubricating Oil (SLO) Polluted Soils Amended with Spiked Organic Fertilizer

Soil contaminations by spent lubricating oil (SLO) have been reported to be threatening as it can negatively impact soil macro/micro-flora, destroy the food chains, disrupt biogeochemical cycling of elements, thus reducing soil fertility/productivity, with attendant economic implications. This study evaluated the changes in microbial population and performance of plant in SLO polluted soils amended with different organic fertilizers. The fertilizers were produced from organic waste materials using aerobic composting technique; pollution was simulated in potted soils; soil toxicity were determined using Zea mays L. as test crop; microbial counts and physicochemical properties of the test soils were determined using standard microbiological and chemical protocols respectively. Apart from significant (P˂0.05) decrease in population of total heterotrophic bacteria (THB) and total fungal counts (TFC) (2.6×108 to 6.1×107 cfu/g and 2.3×105 to 1.7×105 cfu/g respectively), and increase in populations of hydrocarbon utilizing bacteria (HUB) and hydrocarbon utilizing fungi (HUF) (7.3×103 to 4.6×104 cfu/g and 8.0×103 to 1.7×104 cfu/g respectively) following contamination of soil with SLO at pollution level., results also revealed increase (improvements) in counts of all microbial groups at the end of remediation treatments. Mean microbial count in soils amended with different levels of fertilizer treatments (5%, 10%, and 15%) reflected a dose-dependent increase as follows: Ft2 ˃ Ft0 ˃ Ft4 for the 5% (3.7×108 cfu/g), 10% (9.2×107 cfu/g) and 15% (6.9×107 cfu/g) respectively. At 5% application, post remediation pH increased following the order: Ft0 ˃ Ft2 ˃ Ft4 (6.00, 5.34, and 4.90 respectively). The test crop, Zea mays L. recorded 100% and 62.5% germination in amended and unamended soils respectively. Leave length and chlorophyll index of Z. mays L. grown on remediated soils ranged between 35.10±0.40 – 52.85±0.05 (at 5% treatments); 32.60±0.10 – 56.55±0.35 (at 10% treatments); and 35.35±0.15 – 42.45±0.25 (at 15% treatments), compared with 30.30±0.80 – 50.55±0.75 (for PS) and 18.05±0.85 – 25.50±0.70 (for unamended CS). All test crops yielded except those grown on unamended soils. Conclusively, application of organic fertilizers to SLO polluted soils increased population of different groups of soil microbes, leading to increased breakdown of the pollutant and reduced soil toxicity.

Construction of the Stable Lubricant Film on One-Dimensional Cone-Structured Surfaces for Directional Liquid Transport.

Directional liquid transport along one-dimensional structures finds vast applications in fog harvest, liquid separation, sensing, chemical synthesis, and numerous other scenarios. Dynamically, the liquid transport speed is boosted by the driving force and retarded by the hysteresis from the liquid/substrate interface. A capillary force-relied lubricant film or a covalently attached polymer brush on the surface could increase liquid mobility temporarily by reducing the interfacial hysteresis. However, the easy depletion of the lubricant film and the stringent restriction of the substrate severely hamper droplet's directional transport in a long run. Herein, we report a feasible and durable hysteresis reduction design with the polymer-brush stabilized lubricating surface (PBSLS). The PBSLS is achieved through incorporating liquid-like polydimethylsiloxane brushes (b-PDMS) and the liquid PDMS oligomer (o-PDMS). The covalent attached b-PDMS "locks" the lubricant oil o-PDMS to the cone surface via strong intermolecular van der Waals force in between. The PBSLS on the cone surface can be sustained under constant shearing force from liquid transport for at least 6 h. A cone with such PBSLS shows increased ability of droplet transport and enhanced fog collection performance in the long run. This design supplies an effective way toward regulating macro-level interfacial performance through surface design on the molecular level.

Durability Criterion for Lubricant Oils Alloyed with Micro/Nanoparticles of Insoluble Friction Modifiers

Durability Criterion for Lubricant Oils Alloyed with Micro/Nanoparticles of Insoluble Friction Modifiers

Role of Lubricants in Industry: A Review

Lubricants are available in our daily lives for functioning as coolants, to dissipate heat and lubricate different surfaces which can be either in solid, liquid or gaseous forms. It reduces friction by the formation of thin film between two surfaces in contact and by improving efficiency and reducing wear. For any system to work efficiently and effectively appropriate lubricant is needed. Fresh lubricating oil needs to meet specifications of Original Equipment Manufacturers (OEMs). Applying lubricant regularly on tool increases life on usage and durability but a situation comes when the oil starts degrading may be due to depletion of additives or tool break down. Degraded oil is tested by using different physicochemical properties and also by employing different sophisticated analytical techniques like infrared spectroscopy (FTIR), Gas chromatography (GC), Inductively coupled plasma atomic emission spectroscopy (ICPAES), etc. In this article, we shall discuss some basics of lubrication, different lubrication regimes and various kinds of lubricants used for various industrial and automotive applications. Some case studies of oil and also their representative formulations, testing and interpretation of results is being presented for understanding of various lubricants.

Synergetic effect of liquid fuel derived from various waste feedstocks on performance, combustion and emission in a compression ignition engine

ABSTRACT Diesel engines being predominant in transportation sector are limited in addressing the sustainable development goals. The pressing need of environmental concern and fossil fuel depletion enforces the research community toward search of alternative fuels. In such context, waste materials have emerged as a promising feedstock for producing sustainable alternatives for diesel, given their abundance and their significance in waste management. Consequently, in this work, the waste feedstocks identified were waste plastics, waste lubrication oil, waste animal fat obtained from tanneries, waste cooking oil and waste tyres. For extraction of oil from these plastics, lube and tyre oil, pyrolysis was used and transesterification process was adopted for extraction of DLF from waste animal fat and waste cooking oil. The collected DLF was given for fuel property testing and found to be at par to utilize in a CI engine. It was then blended with diesel in the form of B80 (80% DLF and 20% diesel) and named as WTO B80, WLO B80, WCO B80, WPO B80 and WAF B80. To identify the differences in various parameters like combustion, performance and emission of CI engine at various engine loads, a bench test of a single-cylinder direct injection diesel engine without engine modification was done. The blend B80 of waste oil is analyzed in this work for its combustion characteristics and emission of various gases like nitrogen oxide (NO), carbon dioxide (CO2), carbon monoxide (CO), hydrocarbons (HC) and smoke. Among various liquid fuels tested, WPO B80 blend resulted in 32.81% BTE with NO emission of 1885ppm. The results also show emission of 67.2% of smoke, 0.18% of CO and 48 ppm of HC. The cylinder peak pressure for WPO B80 was at 72.85 bar and 48.04 J/deg CA peak heat was released, which concludes it as a suitable fuel for diesel engine compared to other fuels without any engine customization.

A Comparative Analysis of the Lubricating Performance of an Eco-Friendly Lubricant vs Mineral Oil in a Metallic System

Eco-friendly lubricant research continues to increase since it has a comparative performance to commercial mineral lubricants to overcome the effects of environmental impact. However, the efficiency of these green lubricants depends on specific applications. In this study, we analyzed the friction and wear performance of a castor/sesame oil mixture as an eco-friendly lubricant and its comparison to a commercial mineral lubricant tested in a metallic system employed in bearing elements. For this purpose, AISI 8620 steel against ISO 100Cr6 was used as tribological pair. The friction and wear tests were carried out through a Tribometer of ball-on-disk configuration under boundary lubricating conditions, whereas the worn surfaces were investigated by using optical and electron microscopy. The physical properties and the rheological properties of the lubricants were also determined. The friction and wear performance between the eco-friendly lubricant and mineral oil were similar so that the CLE were comparable. The CLE values in terms of friction and wear ranged from 86% to 99.4%, respectively.

CeO2-decorated reduced graphene oxide for lubricative, anticorrosive and photocatalytic purposes

CeO2 decorated reduced graphene oxide (CeO2@rGO) nanocomposites synthesized using a hydrothermal method were studied for their tribological, anti-corrosive and photocatalytic applications. Results showed that CeO2 nanoparticles with an average diameter of ∼12.24 nm were uniformly distributed and covalently bonded onto the surface of rGO. When the nanocomposites were added into PAO5w-40 lubricating oil, the coefficient of friction in the friction test was 31.9% lower than that using the pure lubricating oil. The corresponding wear mechanism was changed from oil-film lubrication to reaction film lubrication, which is mainly attributed to the filling effect of nanostructured CeO2 powers and lubrication effect of rGO. The nanocomposites were also added into chromium-free Dacromet coating and the corrosion current density in the corrosion test was decreased by an order of magnitude. This is mainly due to the formation of various chemical bonds and passivation layer on the modified coating, which improves its density. It is also attributed to the uniformly dispersed rGO, which forms a conductive channel, resulting in the preferred corrosion of the Zn–Al alloy in the coating thus achieving an effective protection effect to the substrate. When the composites were applied as the photocatalyst in an RhB solution under the irradiation of ultraviolet light, the RhB dye was effectively removed with an efficiency up to 90.5%, because the rGO can extend the life time of active electron-hole pairs and prevent CeO2 nanoparticles from severe agglomeration.

Facile fabricant of slippery lubricant-infused porous foam-like surface for efficient fog harvesting

Inspired by pitcher plant, a variety of lubricant-infused surfaces have been created with unique properties. Owing to its high heat transfer performance and negligible contact angle hysteresis, the lubricant-infused surfaces are employed in fog harvesting. However, the loss of lubricant oil can result in performance degradation. Therefore, many surfaces with fine micro/nano structure have been created to increase the lubricant retention ability of lubricant-infused surface. Unfortunately, the procedures for preparing these surfaces are difficult or time-consuming. In this study, we synthesized a porous foam-like lubricant-infused surface (F-LIS). Porous copper foam was created on the surface of copper sheets through the dynamic bubble template method, and the pore walls were made of closely interlaced needle-like nano-dendrites. The fog harvesting efficiency of the surface can reach 2761.2 mgcm−2h−1. Additionally, F-LIS demonstrates excellent mechanical durability and chemical stability as a result of the micro/nano structure and the strong intermolecular force between PFPE as lubricant and the modifier layer, PFDT. After high-speed rotation, prolonged placement and UV irradiation etc., the surface still exhibits brilliant sliding ability and fog harvesting efficiency. This work offers a simple and effective approach for fabricating lubricant-infused surfaces with distinguished fog harvesting capability, providing a reference for relieving the crisis of freshwater resource scarcity.

Double Immobilized Superhydrophobic and Lubricated Slippery Surface with Antibacterial and Antifouling Properties.

A "double immobilized" superhydrophobic and lubricated slippery surface was prepared by simultaneously immobilizing lubricating oil and bactericide molecules. The coordination function of metal organic frameworks (MOFs) was utilized to immobilize trimesic acid, a fungicide, as a ligand of the MOF by the cathodic electrodeposition technique. Aminated silicone oil was used as a lubricating oil and was immobilized to the superhydrophobic MOF film by the curing reaction with isocyanates. This technique is a facile strategy to conductive substrates for fabricating superhydrophobic and lubricated slippery surfaces with satisfactory antibacterial and antifouling properties.

Experimental investigation of the effects of boron oil additive in internal combustion engine

Using additives to engine oils increases engine performance, extending engine maintenance life, boosting the competitiveness of mineral-based oils technically and economically. In this study, the effects of liquid boron oil additive added to mineral-based 10 W-40 engine lubricating oil used in a single-cylinder diesel engine were investigated. 15 % of the engine oil volume was added to the engine as an additive. Experimental studies were carried out at three different engine speeds (i.e., 1500, 1750, and 2000 rpm). The engine, on which no changes were made, was first run with mineral lubricating oil, and then the experiments were repeated with mineral lubricating oil with 15 % boron additive. In the studies, engine torques, specific fuel consumption, and exhaust emissions (HC, CO, CO2, and NOx) were evaluated. In addition, the effects of operating the engine for 100 h without adding any additives and with oil additives containing 15 % boron were also investigated. It was found that engine torque and EGT increased while BSFC, CO2, HC, and NOx decreased in boron-added mineral lubricating oil for all revolutions. In addition, there was a general decrease in CO emissions. In-cylinder SEM images and oil analyses, which were operated with a 15 % boron additive to the engine oil, showed that the boron additive positively affected the engine.

A Multi-Contaminants Detection Sensor Based on Digital Lock-In Amplifier Module With High Sensitivity and High Detectability

Wear debris monitoring in lubrication oil has emerged as a promising solution for health monitoring and fault diagnosis of mechanical equipment. However, the debris feature signal is weak and overwhelmed in the noise. Furthermore, the traditional inductive detection sensors suffer from poor detectability to distinguish non-ferromagnetic metal particles. To address these problems, in this paper, a triple-coil inductive debris sensor combined with a digital lock-in amplifier (DLIA) module was proposed to detect and distinguish multiple contaminants in hydraulic oil so as to achieve high sensitivity and high detectability. First, we introduced the sensor design and fabrication. Second, the triple-coil inductive debris sensor model, the DLIA principle, and the performance analysis of suppressing noise for lock-in amplifier were provided, respectively. Finally, both simulation and experimental platforms were built to substantiate the effectiveness of the proposed approach. Experimental results showed that the detection limit of the designed sensor for iron, copper, and aluminium particles could be inferred as 85.4 μm, 102.4 μm, and 111.6 μm, respectively.

Effect of silver/polydopamine graphene oxide as lubricating oil additive on temperature rise and vibration of motorized spindle

In this study, polydopamine and silver-modified graphene oxide (Ag/PGO) were prepared using a one-step method, and the effects of Ag/PGO as a lubricating oil additive on the viscosity, thermal conductivity, and lubricating performance of lubricating oil were studied. The influence of additive lubricating oil on the temperature increase and vibration of a high-speed motorized spindle was studied through a motorized spindle experiment. The results showed that the addition of Ag/PGO nanocomposites could improve the thermophysical properties and lubricating properties of the lubricating oil. The Ag/PGO nanoparticles deposited on the friction surface formed a friction protective film, which prevented direct contact between the friction pairs and effectively reduced the heat generated through friction and micro-peak collision during bearing operation. The lubricating oil containing Ag/PGO had high thermal conductivity and a good heat dissipation effect in convection heat transfer in the bearing cavity. The deposition and repair of nanoparticles could improve the micro-morphology of the friction surface and reduce the high-frequency amplitude of the motorized spindle.

Impact of the Lubricant on a Modified Revolving Vane Expander (M-RVE) in an Organic Rankine Cycle System

The expansion device is the critical component of micro-to-small scale organic Rankine cycle (ORC) systems, substantially affecting system efficiency and cost. Low isentropic efficiency and lubrication requirements are the main issues associated with using volumetric expanders in ORC systems. Despite lubrication contributing to reducing internal leakages in an expander, it may compromise the performance of the ORC system by adversely affecting the evaporator’s thermal capacity. This study tests a recently developed and modified revolving vane expander (M-RVE) in a micro-scale ORC test rig by implementing an adjustable oil mass flow rate. The impact of the lubricant oil on the performance of the M-RVE prototype is investigated within a wide range of oil circulation rates (OCR). The results demonstrate a negligible improvement in the filling factor for OCRs higher than 1%. Moreover, the shaft power is not considerably sensitive to OCR, while the calculated isentropic efficiency of the expander improves with OCR. Furthermore, the impact of the lubricant oil on the performance of the evaporator is studied, assuming the exact OCR as the expander and measured temperature and pressure similar to the pure refrigerant for the lubricant-refrigerant mixture in the evaporator. The study shows that the evaporator capacity is penalized with OCR, especially for values higher than 1%. Hence, an OCR of about 1% is a good compromise, and it can be used as a guideline for designing revolving vane expanders for micro-scale ORC systems without a dedicated lubricant oil circuit.

Graphene Enhances the Loading Capacity and Lubrication Performance of Ionic Liquids: A Molecular Dynamics Study.

Ionic liquid (IL) combined with graphene additives have garnered extensive attention in the field of high-performance lubricating materials. However, the ambiguous mechanism of graphene influencing the load-carrying and anti-wear capacity of ILs needs further study. In this work, friction simulation shows that adding graphene causes friction coefficient to reduce by up to 88% compared with pure ILs, but lubrication performance is lost due to the destruction of graphene under high stress. Meanwhile, multilayer graphene has better friction-reducing performance and friction durability as compared to the monolayer structure, which is attributed to the easy-shear property and the reduction in the percentage of high tensile stress sites in multilayer graphene structure. In addition, it was found that excessively thick ILs film would form a three-body abrasive wear structure with graphene, which accelerated the structural destruction of graphene and caused a decline in its tribological properties. It is believed these findings can be valuable for designing of high-performance lubricating oil for practical engineering.

Comparative study of influence of molecular structure of hydrogenocarbonate contaminants in adsorption process, using cactus pear forage (Opuntia fícus) as biomass

This work used adsorption technique to evaluate adsorption efficiency of an easily accessible biomass in Paraiba, cactus pear forage (Opuntia fícus), to remove organic contaminants from water/lubricating oil and water/diesel oil systems present in water bodies. Study was developed to obtain kinetic curves to characterization of adsorption dynamics of lubricating oil and diesel oil in contact with biomass. For this, methodology described by Lima et al. (2014), which used mandacaru biomass (Cereus jamacaruna) in particulate form to remove gasoline/diesel mixture, which consisted of: preparing biomass on particulate form, for further granulometric analysis, using sieves; conducting experiments to investigate adsorption kinetics and to obtain adsorption isotherms to complementation of equilibrium study. In despite low adsorption values confirmed by kinetics and equilibrium adsorption graphs, at some points 50% of adsorbed lubricating oil was obtained, which may characterize cactus pear forage as a relatively efficient adsorbent. Low values obtained on adsorption of diesel oil may have been influenced by molecular structure of diesel, constituted of long chains that may have favored oscillations on adsorption by means of cactus pear forage biomass.

Investigation on two-phase flow characteristics and oil capture performance of axial oil scoop in aero-engine

Due to the improvement in the performance of aero-engines and the continuous size reduction, efficient under-race lubrication is becoming more and more important to provide the proper amount of lubricant oil for the main shaft rolling bearings. In this paper, experimental tests and numerical simulations are conducted to investigate the two-phase flow behavior and oil capture performance of the axial oil scoop. It is found that the oil capture efficiency increases with the decrease of injection distance, while the maximum increment of oil capture efficiency is less than 1.5% within the range of 58 mm–128 mm. The measurement results show that the oil capture efficiency first rises to the maximum value of 100% with increasing rotational speed, and then keeps the maximum value constant. Adjusting the oil supply pressure difference can reduce the oil loss and improve the oil capture performance. The oil capture efficiency decreases with increasing jet angle, and the oil capture efficiency corresponding to jet angle of 15° decreases by more than 20% at the rotational speed of 15000r/min. The experimental results are used to develop a corrected discharge coefficient formula based on the rotation coefficient. The predicted results from this formula have a maximum relative error of less than 6%.

A Review on Recycle of Waste Lubricant Oil and its Properties Enhancement

Abstract: Continuous use and disposal of lubricating oil causes land, water and air pollution and also increases dependence on crude oil. This is the reason for the spread of disease, which affects every living being. Reuse of waste oil is the easiest option to avoid such pollution and dependence on crude oil. Another benefit of reusing waste oil is converting waste into money. Recycling waste lubricating oil has become an increasingly important aspect of sustainable waste management and resource conservation. Lubricant oil is made with 90% of base oil and rest of additives. In the lubricant oil, Base oil is never spoiled but after continues use of lubricating oil, it loses their properties because of continues friction, heavy load, and dirt metals absorbed hence it’s become waste oil. Here, we review the methods available to recycle the waste oil with the help of various treatment including acid treatment, clay treatment, adsorption, and solvents. The viscosity modifiers and additives used to make the SAE (Society of Automotive Engineers) grade recycled oil have also reviewed.

Results of modelling the effect of temperature on the thickness of the surfactants layer

Problem. Earthmoving machines operate under high loads, so their tribo-joints periodically operate under unsteady load conditions, which leads to their increased wear and, as a result, a rapid decrease in the residual service life of the units and the reliability of the machines in general. Under unsteady load conditions, friction in the joints of hydraulic drive elements occurs under the boundary lubrication regime. This lubrication mode occurs at high contact loads, high temperatures in the contact zone, and relatively low sliding speeds of the mating surfaces. The combination of boundary lubrication and high dynamic loads often leads to partial destruction of the boundary layer. This leads to direct contact of individual micro-irregularities of the friction surfaces, which is accompanied by a wear process. Hence the importance of the quality of both the parameters of the surface layer of friction surfaces and the parameters of the applied lubricant (oils, working fluids) on the strength and wear resistance of hydraulic drive elements. Goal. The aim of this work is to determine the effect of temperature and radius of curvature of a microroughness on the thickness of the layer of surface-active substances adsorbed on it. Methodology. The solution of the tasks involved the formation of a model of adsorption-desorption equilibrium in the system "working fluid - micron-surface", taking into account the ambient temperature, and its application to determine the dependence of the thickness of the adsorbed surfactant layer under conditions of temperature change. Results. The thickness of the adsorption layer depends mainly on the size of the adsorbing surface field and the energy of thermal vibrations of molecules. It decreases with increasing PP and increases with increasing radius of curvature of the micron roughness. The change in the thickness of the adsorption layer of surfactant molecules on the surface of the micron roughness with a change in the temperature of the RS is not uniform. With an increase in the PP temperature within 300...400 K, the thickness of the adsorption layer of surfactant molecules on the surface of the micron roughness decreases by ~24 %. With an increase in the temperature of the PP in the range of 400...450 K, the thickness of the adsorption layer of surfactant molecules on the surface of the microroughness decreases by ~76 %. The formation of a surfactant adsorption layer on the surface of the microroughness at a temperature above 443 K stops. Originality. A model of the formation of a surfactant adsorption layer on the surface of a separate microroughness on the basis of adsorption-desorption equilibrium in the system "working fluid - microroughness surface" was proposed, taking into account the ambient temperature, which allows us to analyse the nature of the temperature effect on the thickness of the adsorbed surfactant layer. Practical value. The use of the proposed mathematical model makes it possible to estimate the parameter of the surfactant adsorption layer on the surfaces of microroughnesses and rough friction surfaces based on the ambient temperature and the geometry of individual microroughnesses.

Assessment of the Impact of Lubricating Oil Contamination by Biodiesel on Trunk Piston Engine Reliability

The rheological, ignition, and tribological properties of lubricating oils diluted with biodiesel were analyzed. The flash point tFP, calculated cetane index CCI, density ρ, coefficient of the temperature density change ε, kinematic viscosity ν, dynamic viscosity η, viscosity index VI, and lubricity during a High-Frequency Reciprocating Rig (HFFR) test (x, y, WSD, and WS1.4) and lubricating conditions during an HFFR test (oil film resistance FILM and friction coefficient μ) were determined. The test was performed for the oil mixtures of the lubricating oil of the SAE 30 and SAE 40 viscosity grades, which were diluted with the biodiesel blend (D93B7—diesel oil with 7% v/v fatty acid methyl esters, FAME) at concentrations of diesel oil in the mixture equal to 0% (pure lubricating oil), 1%, 2%, 5%, 10%, 20%, 30%, 50%, and 75% m/m, respectively. The experiment confirmed the existence of clear relationships between the increase in the dilution of lubricating oil with tested biodiesel blend and tFP, ρ, ε, ν, η, and VI, and the deterioration of lubrication conditions. It is recommended to take remedial action even in the case of low diesel oil concentration (<5% m/m) in the lubricating oil due to tFP, ν, and η changes. Simultaneously, the tests showed no significant effect on the lubricity and the CCI. The critical contamination of oil with fuel in the range of 2–5% by weight, as indicated in the literature, still allowed for a certain “safety margin” regarding these parameters. However, when the concentration of diesel fuel in the lubricating oil exceeded 5–8% m/m, the deterioration of the lubrication was expressed by a decrease in FILM and an increase in μ was observed; hence, such a contamination should be considered excessive. When the concentration of diesel fuel exceeds 10% by weight, there is a serious risk of engine damage during operation.