Low-viscosity Oil Research Articles

Modelling the impact of reducing lubricant viscosity on a conventional passenger car fuel economy and wear protection

This study explores how reducing lubricant viscosity affects fuel economy in passenger cars through experimental characterization and semi-predictive modelling. Thus, three engine oils (0W-20, 5W-30, and 5W-40) were tested for their rheological and tribological properties. Data were introduced into a detailed GT-Suite model of a turbocharged gasoline SUV. Simulations over six different driving cycles, including European homologation and real-driving conditions, used a fast-running model (FRM) to assess engine friction and wear protection. Results showed that lower viscosity oils, especially 0W-20, significantly reduced frictional losses, enhancing fuel economy. However, lower viscosity also increased contact friction under high power demand, raising durability concerns. A comprehensive evaluation of lubricants performance, offering insights into the trade-offs between fuel economy improvements and potential durability risks.

Superior anti-icing performance of a silicone-based slippery gel coating with a self-replenishing lubricant layer under airflow

Icing phenomena lead to energy consumption, mechanical failures, and potential human casualties. These issues often occur under dynamic airflow conditions. While superhydrophobic (SHPo) surfaces effectively delay ice formation under airflow, they cannot completely prevent it without external energy. This study proposes a long-chain entangled polydimethylsiloxane (LEP) gel coating infused with a lubricant, as an excellent anti-icing surface. The LEP gel has a self-regenerative, low-viscosity oil layer, and it shows remarkable droplet mobility, a very low contact angle hysteresis (CAH), and near-zero ice adhesion. X-ray microimaging shows that condensed droplets on the LEP gel move dynamically, while a bare silicone coating exhibits static behavior. This dynamic droplet behavior significantly delays droplet freezing and frost onset. The LEP gel’s anti-icing performance is assessed in a subsonic wind tunnel. Unlike control surfaces on which frost forms immediately, droplets condense on the gel and then slide off, reducing the frost-coverage rate. Notably, at a wind speed of 5.5 m/s, no frost is formed on the gel. The LEP gel’s superior anti-icing performance is attributed to synergistic effects of the lubricant layer and extremely low CAH. These results show that lubricant-infused slippery gel coatings could prevent icing in airflow environments.

Effect of lubricant inertia on textured journal bearing implementing mass conserving (JFO) boundary conditions

Purpose Cavitation plays a significant role in the performance of textured journal bearings. Furthermore, because of the usage of low-viscosity lubricants and the high working speed of machines, it is pertinent to consider the lubricant inertia while analyzing the operating characteristics of bearings. This paper aims to investigate the influence of lubricant inertia in the case of a spherically textured journal bearing, considering both protrusion and dimple texturing and implementing the mass-conserving (JFO) boundary conditions. Design/methodology/approach A novel modified Reynolds equation has been developed to accommodate the effects of lubricant inertia and cavitation. The cavitation is treated by using mass-conserving (Jakobsson−Floberg−Olsson [JFO]) boundary conditions. The governing equation is solved by the Gauss−Seidel method with successive over-relaxation. To enhance computational efficiency and expedite the convergence process, the progressive mesh densification (PMD) method has been integrated into the solution process. Findings The current study indicates that the JFO boundary conditions result in higher load-carrying capacity and lesser friction variables for heavily loaded bearings, whereas the flow coefficient is reduced due to the application of JFO boundary conditions. The lubricant inertia effect enhances the flow coefficients for lightly loaded and protrusion-textured bearings. Originality/value It is crucial to understand the combined effects of lubricant inertia and cavitation for the effective design of textured journal bearings. The findings from this work will help in designing textured journal bearings more effectively and accurately, particularly when low-viscosity oil is used. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2024-0276/

Simulation method for dynamic characteristics of rotor-support system subjected to environmental loads

An improved finite element method was proposed to investigate the dynamic characteristics of rotor system with environmental loads (temperature and aerodynamic forces) in aeroengines. According to the axial temperature distribution within shaft elements, the polynomials were established for physical properties of material. The derivation for coefficient matrices under thermal loads, and the tensile stiffness matrix considering axial aerodynamic forces were completed, based on the Timoshenko beam theory. A high-pressure rotor was simulated with operating temperature 200∼600∘C, and the magnitude of aerodynamic force is 105N. Furthermore, a squeezed film damper (SFD) was adopted to this rotor-support system, its steady responses were solved by the equivalent coefficient method, and the Newmark-HHT method was utilized to solve the transient responses. The results indicate that the first two critical speeds are reduced by 1.85 % and 2.07 %, which is mainly caused by thermal loads. The rising temperature leads to lower elastic modulus, higher Poisson's ratio and expansion ratio. With the amount of a mass unbalance being 500 g·mm located at the 1st-stage compressor disk (CD1): the 1st resonance peaks at CD1 and turbine disk (TD) increase by 4.56 % and 4.98 %, respectively, and the 2nd resonance peaks at CD1 and TD rise 5.88 % and 5.00 %, separately. Owing to SFD damping, the first two resonance peaks at CD1 and TD decrease by 69 % and 51 %, respectively. Compared to 40 °C, the first two resonance peaks at CD1 increase by 88 % and 55 % at the oil temperature 100 °C. The oil-film damping deteriorates significantly due to the lower oil viscosity in higher temperature. When operating near the first-order critical speed, the transient responses of rotor perform as simple harmonics, circular precession trajectory, dominant rotational frequency, and periodic motions. Overall, the dynamic characteristics of rotor-SFD-support systems exposed to environmental loads can be predicted by the proposed simulation method.

Development of a biomimetic water-based lubricant: Nanoencapsulation of stearic acid using liposomes

Water-based lubricants are abundant in nature; however, they perform poorly in mechanical systems. Based on research into synovial fluid lubrication a water-based liposomal lubricant was developed using a phospholipid (DSPC) and stearic acid (SA). Compared to pure water the liposomal DSPC lubricant improved wear and friction performance, although it underperforms a low viscosity oil such as hexadecane. The inclusion of SA encapsulated within the liposome further improves the performance to a level comparable to hexadecane. Improved performance is achieved due to the following factors: a) DSPC-SA lubricant forms a growing multi bilayer structure in the contact region thereby decreasing wear b) the electrostatic charge associated with the structure allows for retention of the film within the contact area thereby decreasing friction and wear c) liposomes allow for utilisation of insoluble additives within water-based lubricants. The optimal liposomal lubricant tested demonstrates a 63 % reduction of the coefficient of friction and a 99 % reduction in resulting wear compared to DI water alone, thereby providing an avenue for effective utilisation of water in mechanical systems.

Microstructural analysis on the compatibility of various dilution oils on magnetorheological grease performance

This research explores the effects of dilution oils on the storage stability of magnetorheological grease (MRG) by studying the effect of dilution oil viscosity on the microstructure of carrier fluids medium for MRG, which can help address practical challenges encountered in the development and deployment of MRG. Three samples of MRG with 70 wt% CIP are prepared; a control, and 2 samples diluted until 10 wt% hydraulic fluid and kerosene respectively. The resulting samples were analysed using a modular compact rheometer (MCR) for oscillatory strain sweep and rotational current sweep. Rheological analyses were repeated after one year in storage. Fourier-Transform Infrared (FTIR) spectroscopy and Atomic Force Microscopy (AFM) results show significant microstructural and performance deterioration of grease thickener in the sample with kerosene, which concludes that kerosene had a very significant effect on the degradation of the grease thickener. From this study, it was revealed that low viscosity oils disrupt the reconstruction of the thickener of lithium grease, which in turn causes deteriorating shear rheological performance of MRG at off-state conditions. This comprehensive analysis explains the relationships between MRG composition, microstructural characteristics, and performance parameters, offering a foundational framework for further exploration and advancement in this scientific field.

Experimental investigation on the oil extraction process for a novel underground oil storage method: Oil storage in salt cavern insoluble sediment voids

Large-scale underground oil storage is vital for addressing the energy crisis. Leveraging the insoluble sediment space at the bottoms of salt caverns for oil storage is particularly effective in high-impurity salt mines, enhancing oil storage capacity. The process of extracting oil from the sediment void is essential for utilizing this resource. Three experimental devices were developed to investigate this extraction process. We conducted experiments on oil extraction processes and rates for various oil types, analyzing weight changes and influencing factors. The sediment and water content in the extracted oil were also evaluated. Results indicated that extracting oil from the sediment void is feasible, yielding average recovery rates over 90.0 %. High-viscosity oil at 50 °C exhibited three stages: initial stability, a rapid rise, and final stability. Low-viscosity oil correlated with brine injection rates, displaying a rapid rise, stable phase, and subsequent decline. Petrolatum extraction was easier than diesel extraction, and ground temperature improved recovery rates. Changes in water and sediment content had minimal impact on oil quality. This research provides insights for large-scale underground energy storage.

Effect of Grease Composition on Impact-Sliding Wear

Impact-sliding experiments were performed by using four self-made lithium-based greases, namely Yangtze Grease 1, Yangtze Grease 2, Yangtze Grease 3, and Yangtze Grease 4. The influence of base oil viscosity, thickener content, and morphology of thickener fiber clusters on the lubricating state were visually explored, combined with field-emission microscopy and two-light interference technology. The grease film distribution at the middle section was measured using Dichromatic Interference Intensity Modulation (DIIM) software. All experiments were executed in a completely flooded environment. The results show that among the components of grease, the base oil’s viscosity has the greatest impact on the anti-wear performance of the grease. As the viscosity of the base oil increases, the grease exhibits better anti-wear performance. The grease film thickness under the condition of high-viscosity base oil is about 10 times higher than that under the condition of low-viscosity base oil. Secondly, the content of thickener in the grease needs to be controlled within a reasonable range. The experiments indicate that the effect of thickener content on the grease’s film-forming properties becomes more pronounced at higher speeds. From the experiment using YG 4, it can be seen that a higher thickener content under high-speed conditions increases the thickness of the lubricating grease film by about 10 times. The dimensions of the thickener fibers and the density of their entanglement structure significantly influence the rheological properties and load-bearing capacity of the grease. Larger fiber sizes and higher entanglement densities result in reduced grease fluidity and recovery but enhance its load-bearing capabilities. In order to obtain the best anti-wear performance during impact-sliding motion, the size of the thickener fiber and the density of the entanglement structure need to be controlled within an appropriate range.

Wear Performance Evaluation of Polymer Overlays on Engine Bearings.

Modern engine bearing materials encounter the challenge of functioning under conditions of mixed lubrication, low viscosity oils, downsizing, start-stop engines, potentially leading to metal-to-metal contact and, subsequently, premature bearing failure. In this work, two types of polymer overlays were applied to the bearing surface to compensate for extreme conditions, such as excessive loads and mixed lubrication. Two different polymer overlays, created through a curing process on a conventional engine bearing surface with an approximate thickness of 13 µm, were investigated for their friction and wear resistances under a 30 N load using a pin-on-disc setup. The results indicate that the newly developed polymer overlay (NDP, PAI-based coating) surface has a coefficient of friction (COF) of 0.155 and a wear volume loss of 0.010 cm3. In contrast, the currently used polymer overlay (CPO) in this field shows higher values with a COF of 0.378 and a wear volume loss of 0.024 cm3, which is significantly greater than that of the NDP. It was found that, in addition to accurately selecting the ratios of solid lubricants, polymer resins, and wear-resistant hard particle additives (metal powders, metal oxides, carbides, etc.) within the polymer coating, the effective presence of a transfer film providing low friction on the counter surface also played a crucial role.

Quinoa starch-based Pickering emulsions with small-molecule oil solvents: Exploring solvent varieties and depletion attraction

The successful preparation of starch-based Pickering emulsions typically relies on the use of high-viscosity or high-boiling-point oil solvents. However, these solvents present challenges in removal and limit the applicability of the emulsions. This study aims to investigate the feasibility and effectiveness of employing small-molecule solvents as alternatives for the oil phase. Specifically, quinoa starch granules are used as the emulsifying agent, with a systematic exploration of various small molecules from different solvent categories. This research contributes by identifying the impact of solvent-particle interactions on the feasibility of emulsion formation—an aspect critical but often overlooked in previous discussions on solvent influence on emulsion quality, essential for guiding solvent selection. Furthermore, to address potential challenges associated with maintaining emulsion stability when using low-viscosity oils, a strategy based on exploiting depletion attraction is proposed and demonstrated, leveraging bovine serum albumin as depletants.

Research on Component Variation and Factors Affecting Minimum Miscible Pressure in Low Viscosity Oil Miscibility Process.

Miscible gas flooding is an important approach for enhancing the recovery of unconventional oil reservoirs. The injected gas and crude oil components has a significant impact on the minimum miscible pressure. In order to clarify the miscibility characteristics and factors influencing the minimum miscibility pressure, combining PVT and slim tube experiments, the minimum miscibility pressure between Tuha low viscosity oil and different injected gas was measured. Additionally, chromatography experiments were conducted to study the composition changes of produced oil. The results indicate that when the injection pressure is higher than the minimum miscible pressure, the extraction effect of injected gas on heavy fraction (C16+) in crude oil is enhanced and the extraction effect on light alkanes (C1-C6) is reduced. The increase in the content of light alkanes (C1-C6) and middle distillates (C7-C15) in crude oil reduces the minimum miscibility pressure between crude oil and injected gas. Pipeline gas can effectively extract heavy fraction from crude oil, but its breakthrough time is early. Under the same pressure, earlier breakthrough time of injected gas makes it more difficult for the crude oil and injected gas to miscible. Through the analysis of experimental results, the following main conclusions are drawn: Immiscible flooding causes heavy fraction (C16+) in crude oil to remain, which might affect the physical properties of the reservoir, increasing the difficulty of subsequent development. Gas fingering phenomenon significantly influences the miscibility of injected gas and crude oil, and the viscosity ratio of injected gas and crude oil under high-pressure conditions can be used as an important criterion for screening injected gas.

Clove oil additives in vegetable oil: an assessment of fuel properties

Vegetable oil, obtained from plants such as coconut or Jatropha curcas, serves as a valuable renewable energy source. Nonetheless, it presents certain limitations in comparison to diesel fuels, namely, low volatility and high viscosity. One straightforward approach to overcome these limitations is the addition of high-volatility oil and low-viscosity oil. In this study, we incorporated 10% clove oil into coconut oil and Jatropha curcas oil. Fuel properties, including density, viscosity, flash point, and heating value, were measured in accordance with international standards. Additionally, Thermogravimetric Analysis (TGA) testing was performed to detect decomposition during the heating process. The findings indicated that the addition of clove oil increases density (from 0.922 g/ml to 0.934 g/ml), while other properties decrease, such as viscosity (from 30.12 cst to 27.7 cst), flash point (from 286°C to 182°C), and heating value (from 37.1 MJ/kg to 35.8 MJ/kg). TGA demonstrated that the inclusion of clove oil resulted in increased decomposition within the temperature range of 200°C–400°C, suggesting that clove oil falls into the category of medium-volatile oils. Although the addition of clove oil were able to modify the fuel properties of vegetable oil, it did not align with the characteristics of conventional diesel fuel and necessitates further modification for practical implementation

Robust superhydrophobic Fe3O4/PAN/PBA nanofibrous aerogel with photo/magneto-thermal properties for efficient all-weather cleanup of viscous crude oil spills

Developing efficient absorbents for the cleanup of highly viscous crude oil spills is of critical importance. The current light-to-heat/electric-to-heat methods to reduce the viscosity of crude oil were limited by the complicated preparationprocesses, weather conditions and potential risk of electrical leakage. Here, a robust superhydrophobic composite Fe3O4/PAN/PBA nanofibrous aerogel (NFA) with excellent photo/magneto-thermal performance for efficient all-weather viscous crude oil spill remediation was fabricated by integrating facile blend electrospinning and freeze-drying techniques. Due to its superhydrophobicity/superoleophilicity (water contact angle of 151.3° and oil contact angle of 0°) and anisotropic microchannelstructure, the composite NFA exhibited rapid adsorption kinetics and ultra-high absorption capacity (54.4 − 97.1 g/g) toward various low-viscosity oils and organic solvents. Meanwhile, it displayed outstanding mechanical recyclability (84.07 % recovery after 200 cycles at 80 % strain) and reusability (86.74 % of theinitial capacity after 10 absorption-squeezing cycles). Notably, the composite NFA also showed excellent photo/magneto-thermal conversion efficiency, allowing it to achieve continuous and efficient cleanup ofcrude oil (recovery rate of 6.67 x103 kg m−3h−1) via peristaltic pumping. Therefore, this material holds great potential for all-weather cleanup of crude oil spills.

Does Engine Oil Type Affect Fuel Consumption in Passenger Vehicles? A Two-Year Investigation

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.

Super-slippery silicone-based gel coating with a regenerative oil layer for long-term prevention of surface contamination

Polymer-based gel-type coatings, in which oil molecules are absorbed within polymer networks, have drawn attention as functional coatings to address fouling problems. However, surface drought caused by lubricant depletion limits the longevity of conventional gel-type coatings. In this study, a super-slippery long-chain entangled polydimethylsiloxane (LEP) gel that can self-regenerate a low-viscosity oil layer is proposed to enhance its long-term anti-fouling performance in both indoor and marine habitats. The proposed LEP gel coating can effectively prevent contamination from numerous liquids and protect aluminum surfaces from corrosion in seawater. Even when it was incubated with Porphyridium purpureum, marine red algae that readily stick to the surface, no biofilm was formed on the coated samples for 37 weeks. In field tests, no biological adhesion was observed on the coating surface which was applied to port structures and left for two summer months. This enhanced anti-contamination performance is mainly attributed to the dual protective barrier comprising the underlying polymer layer and regenerative oil layer. Due to special property of continuous self-regeneration of oil layer, the proposed LEP gel surface demonstrates much enhanced sustainability, compared to conventional gel-type coatings. Consequently, the long-term anti-contamination performance of the super-slippery LEP gel coating would pave the way for novel approach to its practical applications.

Synergistic Effect of Acrylate of Dialkyl Dithiophosphoric Acid Combined with Molybdenum Dialkyl Dithiocarbamate as Additives in Gear Oil

With the aim of improving the tribological properties of low-viscosity gear oil for automobiles, an acrylate of dialkyl dithiophosphoric acid (ADDP) with strong polar groups was synthesized. The tribological behavior of ADDP combined with molybdenum dialkyl dithiocarbamate (MoDTC) in gear oil was systematically studied. Tribological performances of gear oil containing different additives were assessed using a four-ball friction and wear tester. The obtained tribological characteristics reveal that ADDP and MoDTC can significantly improve the antiwear and antifriction performance of low-viscosity gear oil. Moreover, compared with using MoDTC or ADDP alone, the average friction coefficient and wear scar diameter of ADDP combined with MoDTC further decreased by 2.41–19.15% and 5.00–18.19%, respectively. Analysis of the worn surface showed that the structural characteristics and physical synergistic lubricating actions of the ADDP with MoDTC additives during the friction process can contribute to the exceptional tribological properties of the hybrid additives.

Investigation on friction pressure of oil storage and brine discharge in underground salt caverns

The design and control of oil injection and brine removal constitute a crucial task in the construction of salt cavern oil storage (SCOS). In this article, the innovation is that the SCOS pressure governing equations were established, and the impacts of salt cavern depth, crude oil viscosity, as well as injection rate on pipeline friction pressure and wellhead injection pressure were calculated and assessed. Besides, the selection principle of varying viscosity crude oil in different depths of salt caverns, as well as the implementation of an optimal oil injection rate, were proposed. The findings indicated that within the depth range of 500 ∼ 2,000 m, there was a nearly linear correlation between the increase in salt cavern depths and the corresponding rise in injection pressures. The friction pressure generated by the injection pipe constituted the predominant proportion among them, and the range of oil injection pressure was 3.4 ∼ 23.0 MPa. Additionally, the injection pressure and friction pressure were primarily influenced by the viscosity of crude oil, with cavern depth and injection displacement following suit. Shallow salt caverns are optimal for storing high-viscosity crude oil, whereas deep salt caverns are better suited for low-viscosity crude oil storage.

Effect of additive combinations on tribofilm formation in fully formulated 0W‐8 oil

Reducing engine oil viscosity is an effective way to meet automotive fuel efficiency requirements. Clarifying the effects of multiple coexisting additives in low-viscosity oil is important for the development of low-viscosity engine oil. In this study, six kinds of 0W‐8 engine oil, including those without a Ca-derived detergent, a dispersant or molybdenum dialkyldithiocarbamate (MoDTC), were selected to study the effects of these additives on the tribofilm formation and the friction characteristics of fully formulated low-viscosity oil. A custom-made rolling and sliding tribometer was used to evaluate the tribological properties and form the tribofilms. The elemental distribution of the tribofilms was characterized by electron probe microanalysis (EPMA), and the chemical compositions of the films were determined using X-ray photoelectron spectroscopy (XPS). The Ca-derived detergent hindered both the ZnDTP-derived and MoDTC-derived tribofilm formation in the fully formulated low-viscosity oil due to adsorption competition. The effect of the ashless dispersants on the ZnDTP-derived tribofilm formation in the fully formulated 0W‐8 oil showed opposite results in the presence or absence of MoDTC. The addition of MoDTC had different effects on the ZnDTP-derived tribofilm formation under different additive combinations.

Numerical Investigation on Alkaline-Surfactant-Polymer Alternating CO2 Flooding

For over four decades, carbon dioxide (CO2) has been instrumental in enhancing oil extraction through advanced recovery techniques. One such method, water alternating gas (WAG) injection, while effective, grapples with limitations like gas channeling and gravity segregation. To tackle the aforementioned issues, this paper proposes an upgrade coupling method named alkaline-surfactant-polymer alternating gas (ASPAG). ASP flooding and CO2 are injected alternately into the reservoir to enhance the recovery of the WAG process. The uniqueness of this method lies in the fact that polymers could help profile modification, CO2 would miscible mix with oil, and alkaline surfactant would reduce oil–water interfacial tension (IFT). To analyze the feasibility of ASPAG, a couples model considering both gas flooding and ASP flooding processes is established by using the CMG-STARS (Version 2021) to study the performance of ASPAG and compare the recovery among ASPAG, WAG, and ASP flooding. Our research delved into the ASPAG’s adaptability across reservoirs varying in average permeability, interlayer heterogeneity, formation rhythmicity, and fluid properties. Key findings include that ASPAG surpasses the conventional WAG in sweep and displacement efficiency, elevating oil recovery by 12–17%, and in comparison to ASP, ASPAG bolsters displacement efficiency, leading to a 9–11% increase in oil recovery. The primary flooding mechanism of ASPAG stems from the ASP slug’s ability to diminish the interfacial tension, enhancing the oil and water mobility ratio, which is particularly efficient in medium-high permeability layers. Through sensitivity analysis, ASPAG is best suited for mid-high-permeability reservoirs characterized by low crude oil viscosity and a composite reverse sedimentary rhythm. This study offers invaluable insights into the underlying mechanisms and critical parameters that influence the alkaline-surfactant-polymer alternating gas method’s success for enhanced oil recovery. Furthermore, it unveils an innovative strategy to boost oil recovery in medium-to-high-permeability reservoirs.

Ceresin wax enhances hydrophobicity and density of bio-based polyurethane of controlled-release fertilizers: Streamlined production, improved nutrient release performance, and reduced cost

Bio-based coated controlled-release fertilizers (BCRFs) can significantly improve nutrient utilization and reduce pollution. However, challenges such as spray gun clogging, adhesion and tearing between fertilizers during the actual production of BCRFs pose a severe challenge to production chain development. In addition, the poor hydrophobicity and cross-linking properties of bio-based coatings severely affect the controlled release properties of BCRFs. Although some measures have been taken to ameliorate the above problems, the cumbersome and costly modification process is challenging to be applied on a large scale. Therefore, the primary goal of this work is to search for a more straightforward and efficient method of production and modification to address the aforementioned unresolved challenges in the field of CRFs. In this study, bio-based polyester polyol (BPP) was used as the base for polyurethane reaction, and low-viscosity castor oil (CO) was used as the modifier to reduce the viscosity of BPP. This led to the preparation of Inter-Modified Coated Controlled-Release Fertilizers (ICRFs) to prevent spray gun clogging. Building upon this, hydrophobic and dense wax-based coated fertilizer (WBCF) was prepared by modifying ICRF with Ceresin wax to alleviate the challenges associated with adhesion and tearing between fertilizer particles during the coating process. The WBCF exhibited remarkable controlled-release characteristics, with a nitrogen (N) release longevity of nearly 180 days, requiring only 3 % of the coating materials. This work provides a simple and efficient strategy for overcoming the key constraints in the development and production of CRFs and provides insights into developing green, low-cost fertilizers with excellent controlled-release properties.