Browse Topic: Diesel engine lubricants
Shell Rotella hosted journalists at the National Tractor Pulling Championships in Bowling Green, Ohio, in August, where the company was sponsoring tractors run by Koester Racing in the mini-modified division. Karin Haumann, OEM technical manager of Shell Global Solutions, was onsite and spoke with TOHE about the approaching proposed category 12 (PC-12) heavy-duty diesel engine oil category. PC-12 engine oils are in development and will be licensed for use on January 1, 2027. The current engine oil categories, CK-4 and FA-4, were introduced in 2016. Development of the new category is necessary due to advancements in engine technology, and it aligns with stricter emissions regulations that begin in 2027, said Haumann, who serves as chairperson of the API new category development team. “As diesel engine technology evolves, they require oils that offer increased oxidation performance and wear reduction, can handle higher temperatures, and improve fuel economy,” she said. Lubricant producers also must meet reduced phosphorous and sulfated ash limits, which otherwise can compromise emission control systems and negatively impact fuel economy.
This study examined the friction factor of replaceable element and conventional oil filters in a diesel engine lubrication flow setting, simulated in a precision benchtop facility that was developed for this purpose. Using clean engine oils, pressure drop across the filters was measured as a function of oil temperature and flow rate in the test facility in the range of 100-220°F and 2.0-4.5 GPM typical of diesel engine lubricant flow. The experimental results show systematic differences in the behavior between conventional and replaceable element oil filters attributable to temperature-related permeability variation in the replaceable filter element.
Durability remains a primary concern when formulating heavy-duty (HD) diesel engine oils, but in future there will be increased attention to fuel efficiency, particularly in Europe where the European Commission is proposing the first ever CO2 emission targets for heavy-duty vehicles. Although there are no internationally recognised fuel efficiency tests for HD diesel engines, there have been some regional and OEM developments pushing in the direction of improved fuel efficiency. In Japan the relatively new JASO DH-2F standard adds a fuel efficiency requirement, measuring fuel efficiency using the Hino N04C engine which is also used within the standard for other performance testing. In North America API have introduced the FA-4 performance standard to allow users to specify an xW-30 oil of lower HTHS150 to help achieve fuel efficiency, but with no accompanying test to quantify. In Europe ACEA are planning a HD fuel economy “F” classification which may be something like API FA-4. Volvo and Daimler have developed their own fired engine tests to determine the fuel efficiency effect of the oil. Against this background, we selected the Daimler OM501 fuel economy test as a relevant and important option and used it for the work reported here. A range of multigrade engine oils were formulated for evaluation in the OM501 fuel economy test. In addition to targeting the usual HTHS150°C value of ≥3.5 mPas. normally associated with xW-40 oils used in HD diesel engines, HTHS150°C of ≥2.9 mPas. as mentioned for xW-30 in API FA-4, and also lighter oils of HTHS150°C ≥2.6 mPas were included. In addition, we used a range of different VII (Viscosity Index Improver) types to get a variation in lower temperature viscosity values even when the HTHS150°C values were set as mentioned above. We used group III type base-oil and a suitable DI package throughout and the VIIs used included those recommended for such oils, plus fuel efficient PAMA comb type VIIs. Results broadly show a strong dependence of fuel economy to viscosity in this test. This also applies to the lighter HTHS150°C ≥2.6 mPas. oils which also looked to be providing predominantly hydrodynamic lubrication and so were not improved in fuel economy by the application of organic friction modifier. Furthermore, the viscosity when measured by HTHS80°C and HTHS100°C provided an excellent correlation to fuel economy (R2 ~ 0.98) when viewed as a simple linear plot. All other viscosity values such as HTHS150°C (R2 ~ 0.68) and KV100C (R2 ~ 0.72) did not correlate as well. VI has no correlation to fuel economy. It was demonstrated that oils with the same viscosity protection in terms of HTHS150°C could have a significantly different fuel economy performance due to the differences in HTHS80°C and HTHS100°C brought about by the use of different VII types or different formulation strategies. Clearly, reducing the HTHS80°C and HTHS100°C gives an improvement in fuel economy for this engine. The relationships established in this paper will be of use within the industry in predicting the likely OM501 fuel economy performance in advance of, or instead of actual OM501 testing. The HTHS80°C or HTHS100°C value of the formulation can instead be used to predict the likely OM501 fuel economy result. ails.
In order to meet Corporate Average Fuel Economy (CAFÉ) regulations and Bharat Stage VI (BS VI) emission regulations, Indian auto original equipment manufacturers (OEMs) are adopting low viscosity engine/axle/transmission oils to achieve overall fuel efficiency gain. Attaining fuel economy by reducing oil viscosity is already established for passenger car motor oils (PCMOs) but is in its initial phase for heavy-duty diesel engine oils (HDDEOs). Now SAE 15W-40 is the most widely used viscosity grade by volume for HDDEO. In India, a large number of old vehicles meeting BS II, BS III and BS IV norms exists and require sustainable strategy to reduce fuel consumption, as well as overall greenhouse gas emissions. In this paper, authors discussed the development of low viscosity heavy duty diesel engine oil in 10W-30 viscometrics meeting API CH4 specification. Fuel economy credential of the developed product was carried out on a chassis dyno w.r.t. the reference oil in “Delhi Bus Driving Cycle (DBDC)”. The authors also studied the effect of viscosity on the engine durability by mileage accumulation test of 40,000 kms run in chassis dynamometer by monitoring engine wear in used oil analysis. Finally to check the fuel economy benefit and oil performance in field, a field trial was conducted on old BS II and BS III buses in two bus depots. Fuel economy (FE) was calculated based on the KPTL (kms per ten lts) value of the candidate oil w.r.t. the reference oil. From the trial data it was established that low viscosity engine oil provides adequate durability with sustained fuel economy. However, the FE has direct bearing on driving conditions and more stop/go condition affects fuel economy benefits.
Erratum
This study employed a diesel particulate generator (DPG), with an installed engine oil injector for soot and ash accumulation in a diesel particulate filter (DPF). Ash was generated by engine oil injection into the diesel burner flame. The amount of soot accumulation per loading varied from 0.5 g/L to 8 g/L while ash accumulation amount per loading was maintained at 0.5 g/L. Initially, ash accumulation distribution in the DPF was visualized using X-ray computed tomography (CT). It was revealed that the form of ash accumulation changed depending on the amount of soot accumulation before active regeneration, i.e., a large amount of soot accumulation resulted in plug ash, whereas a small amount of soot accumulation resulted in wall ash. To clarify ash accumulation mechanisms, soot and ash transport behavior in DPF during active regeneration process was directly observed using a high-speed camera through an optically accessible D-shaped cut DPF covered with a quartz glass plate. From the results, it was found that for larger amounts of soot accumulation, the lump of soot in the soot cake layer was transported toward the end plug of the DPF. On the other hand, for smaller amounts of soot accumulation, the lump of soot was not formed in the soot cake layer. Soot was oxidized on the spot and gradually disappeared. In addition, it was found that once the wall ash was formed, the lump of soot could be transported easily, even with a lower amount of soot accumulation.
During diesel engine operation, some fuel is entrained in engine oil, particularly as a consequence of strategies to regenerate NOx traps or particle filters. This “fuel dilution” of oil can adversely affect engine oil properties and performance. Compared to diesel fuel, biodiesel is more prone to fuel dilution and more susceptible to oxidation. Oxidation stability experiments were conducted at 160°C using a modified Rapid Small-Scale Oxidation Test (RSSOT) and a Rancimat instrument with 0, 5, 10, and 20 wt% biodiesel in four fully formulated engine oils, two partially formulated engine oils, and two base oils. These experiments showed decreasing oxidation stability with increasing biodiesel content. An exception was noted with the least stable oils (two base oils and one engine oil) in which 5 wt% biodiesel improved the oxidation stability relative to oil without biodiesel. Experiments with biodiesel distillation fractions identified this stability enhancement within the least volatile biodiesel fraction, consistent with natural antioxidants in the biodiesel. Omission of two engine oil additives, antioxidants and zinc dialkyldithiophosphates (ZDDP), led to an unexpected increase in oxidation stability (with and without biodiesel). Time-series oxidation experiments at 160°C with one of the fully formulated engine oils, with and without 20 wt% biodiesel, demonstrated that the biodiesel caused greater oxidation instability and extent of oxidation, greater formation of peroxides and reduction in total base number (TBN), increased ester content, and higher density. Kinematic viscosity increased with aging time and eventually surpassed that of the engine oil aged without biodiesel. With extended aging time, the fully formulated engine oil containing biodiesel “broke,” forming black tar-like materials with high viscosity.
Modern agriculture has evolved dramatically over the past half century. To be profitable, farms need to significantly increase their crop yields, and thus there are amplified demands on farming equipment. Equipment duty cycles have been raised in scope and duration, as the required output of the agricultural industry to sustain a growing population has stimulated the need for further advances in effective productivity gains on the farm. The mainstay mechanical assistant to the farmer, the tractor, has also evolved with the changes in modern agriculture to meet the requirements of these newer tasks. Larger, more capable vehicles have been introduced to help farmers efficiently meet these demands. At the same time, the current generation of tractor diesel engine lubricants has facilitated high levels of performance in the agricultural equipment market for many years. This is a testament to the role modern lubricants play in productivity in such a critical industry. With a growing global population to feed, and government regulations requiring reduced emissions for off-highway (OH) equipment, it is important to become more efficient in the ability to grow sufficient crops. One area worth investigating is the impact of engine lubricants on fuel efficiency. To quantify the improvement in fuel efficiency, full-scale farm tractor tests were conducted at the Nebraska Tractor Test Laboratory (NTTL). The scope of the experiment was to evaluate observable vehicle fuel economy improvements provided by various fresh engine oils. Testing showed improvements in specific fuel consumption (SFC) of nearly 2% when comparing an American Petroleum Institute (API) FA-4 oil to an API CJ-4 baseline. Furthermore, a strong relationship between high-temperature high-shear viscosity (HTHS) and SFC was observed.
As fuel economy becomes increasingly important in all markets, complete engine system optimization is required to meet future standards. In many applications, it is difficult to realize the optimum coolant or lubricant pump without first evaluating different sets of engine hardware and iterating on the flow and pressure requirements. For this study, a Heavy Duty Diesel (HDD) engine was run in a dynamometer test cell with full variability of the production coolant and lubricant pumps. Two test stands were developed to allow the engine coolant and lubricant pumps to be fully mapped during engine operation. The pumps were removed from the engine and powered by electric motors with inline torque meters. Each fluid circuit was instrumented with volume flow meters and pressure measurements at multiple locations. After development of the pump stands, research efforts were focused on hardware changes to reduce coolant and lubricant flow requirements of the HDD engine. As engine hardware changes were made to reduce coolant and lubricant requirements, the fuel economy benefit was immediately realized. Several hardware sets are discussed along with the resulting reduction in pump parasitic losses. Lastly a comparison is made between the production engine configuration and an optimized setup with several new engine technologies for reduced parasitic losses and increased Brake Thermal Efficiency (BTE).
An unprecedented global focus on the environment and greenhouse gases has driven recent government regulations on automotive emissions across the globe. To achieve this improvement, Original Equipment Manufacturers (OEMs) have advocated a progressive move towards the use of low viscosity grade oils. However, the use of lower viscosity grades should not compromise engine durability or wear protection. Viscosity modifiers (VM) - polymeric additive components used to tailor the lubricant’s viscometric properties - have been viewed as a key enabler for achieving the desirable balance between fuel economy and engine durability performance. Self-assembling diblock copolymers represent a unique class of VMs, which deliver superior shear stability due to their tunable association/dissociation in the lubricating oil. Superior shear stability ensures that the oil viscosity and its ability to offer reliable engine protection from wear is retained over the life of the oil in the engine. In addition, some polystyrene containing diblock VMs can help to boost soot dispersancy due to polystyrene block adsorption onto the soot surface. This additional feature helps in preventing soot aggregation, thereby maintaining lubricant viscosity within desirable range and potentially reducing soot induced abrasive wear in the engine. Here we present a next generation diblock VM designed for high quality base stock applications and its performance attributes in top-tier heavy duty diesel (HDD) formulations. In particular, we demonstrate shear stability and soot dispersancy credits of this VM in bench, engine and field tests, as well as the ability to formulate low viscosity oils without compromising engine durability.
The interest on improving fuel efficiency of vehicles is increasing day by day. Fuel efficiency standard for diesel commercial vehicles such as buses and trucks was published in Japan. Using a fuel efficient engine lubricant is one of the effective paths and there are several 5W-30 diesel engine lubricants in Japanese market which are advertised to give a benefit on fuel efficiency against 10W-30 oil. During the development of 5W-30 fuel efficient diesel engine oil, it was revealed that the piston underside was significantly blackened by the detergency engine test (JASO M 336: 2014). In this paper, the causative agent which blackened the piston underside was investigated and the formulation to inhibit this blackening phenomenon was studied. Through several tests, it was considered that use of poly methacrylate based viscosity index improver and ester type friction modifier deteriorated detergency performance. However, by the addition of glycerol mono oleyl glycerol borate, effects of improving detergency and reducing friction coefficient were observed.
Biodiesel fuel can be used in diesel engines with no major modification, but there are some issues derived from the properties of the fuel. Engine oil dilution is a major issue caused by lower volatility and low oxidation stability in biodiesel fuel. The purpose of this study was to clarify the influence of oil dilution by biodiesel fuel on oxidative degradation characteristics, including the acid value (AV), carbon residue (CR), and kinematic viscosity of diesel engine lubricant oil. Degradation assessment was carried out on lubricant oil during operation of a small diesel engine generator, as well as an oxidative acceleration test using a mixture of biodiesel and lubricant oil. It was found that the kinematic viscosity decreased to 23% from its initial value, the dilution rate increased almost linearly, amounting to 2.8 mass-% after 102 hours of engine operation, and deterioration was greater in JASO DH-1 grade lubricant oil mixed with biodiesel than in JASO DH-2.
In order to study and evaluate the effect of sulfated ash in different diesel engine lubricants on the performance and durability of diesel particulate filter (DPF), the two engine oils of API CI-4 and CJ-4 with different sulfated ash levels are used respectively in the durability tests of two DPF systems. Moreover, the pressure drop, ash loading and filtration efficiency of the two DPFs, deposits in the inlets and outlets of the DPFs, intake flow rate and fuel consumption rates of engine are measured and compared. The test results show that: Compared to the API CI-4 which has more ash in the formulation than the API CJ-4, the API CJ-4 shows a markedly excellent performance on the lower ash loading and longer service interval and life for DPF, as well as lower fuel consumption rate for the diesel engine with DPF.
The aim of this paper is the analysis of a Diesel engine lubrication circuit with a tri-dimensional CFD technique. The simulation model was built using Pumplinx®, a commercial code by Simerics Inc.®, developed and optimized for predicting oil flow rates and cavitation phenomena. The aim of this paper is, also, to show that this code is able to satisfactorily model, in a very “economic” way, an unsteady hydraulic system such as the lubrication circuit First of all, an accurate model of a lubrication circuit oil pump will be described. The model was validated with data from an experimental campaign carried out in the hydraulic laboratory of the Industrial Engineering Department of the University of Naples. Secondly, the oil pump model was coupled with a tri-dimensional model of the entire lubrication circuit, in order to compute all the hydraulic resistances of the network and the oil consumption rate of the circuit components
We studied the influence of extreme pressure (EP) antiwear additive on the emission and distribution of particulate matters (PMs), since EP antiwear additive is necessary to improve the property of lubricating oil with the downsizing development of engines. We used a four-cylinder, turbocharged, and inter-cooled system with SAE15W-40 lubricant diesel engine. Pure diesel and fuel blends with varying weight percentages (0.5%, 1.0%, and 1.5%) of EP antiwear additive were used. Engine speed increased by increments of 400 from 1,200 rpm to 2,800 rpm under medium load and full load. The DMS500 was used to acquire particle data, and the Wave Book was employed to record oil and cylinder pressure. Conclusions drawn from the experiments suggest that EP antiwear additive has significant effects on PM emissions and distributions. Increments and decrements were observed on the number of accumulation mode particles and nucleation mode particles with BDAW-0.5. By contrast, the number of nucleation mode and accumulation mode particles increased when BDAW-1.0 and BDAW-1.5 were burned. The deterioration of accumulated PM enables the absorption of nucleation mode particles; however, the absorption capacity is limited. Thus, the emission of nucleation mode particles was optimized even though the number of accumulation mode particles increased with BDAW-0.5 and deteriorated with BDAW-1.0 and BDAW-1.5. The sulfur content in EP antiwear additive can affect the emission of nucleation mode particles. Furthermore, the high viscosity and flash point of EP antiwear additive can reduce volatility and atomization, significantly influences the emission of accumulation mode particles.
It is expected that the world's energy demand will double by 2050, which requires energy-efficient technologies to be readily available. With the increasing number of vehicles on our roads the demand for energy is increasing rapidly, and with this there is an associated increase in CO₂ emissions. Through the careful use of optimized lubricants it is possible to significantly reduce vehicle fuel consumption and hence CO₂. This paper evaluates the effects on fuel economy of high quality, low viscosity heavy-duty diesel engine type lubricants against mainstream type products for all elements of the vehicle driveline. Testing was performed on Shell's driveline test facility for the evaluation of fuel consumption effects due to engine, gearbox and axle oils and the variation with engine operating conditions. To complement the rig-based testing, a field test protocol has been developed to better understand the linkage between operating conditions and fuel economy changes when driveline lubricants are changed. Two standard, delivery-type, 18-ton trucks have been modified with fuel-flow, engine operation and GPS (global positioning system) measurement equipment. Following a fixed on-road test route in the UK containing city, local, highway and hill driving conditions, the fuel consumption data was separated out for each situation to demonstrate the relative differences. To minimize variability, tight controls were placed on the test set-up, measurements taken and the operation of the vehicles. Using a Mercedes Benz OM 460LA heavy-duty diesel engine run under the World Harmonized Transient Cycle (WHTC) and World Harmonized Stationary Cycle (WHSC), a combination of a SAE 5W-30 engine oil, SAE 75W-80 gearbox oil and SAE 75W-90 axle oil gave average fuel consumption improvements of 1.8% and 1.1%, respectively, relative to a SAE 15W-40 engine oil, SAE 80W gearbox and a SAE 90 axle oil. Using the WHSC cycle, significant variations in the individual lubricant contribution under different speed/load conditions within the cycle were identified. Additionally, an average fuel consumption improvement of 1.8% was observed using medium-duty trucks under a range of typical European driving conditions in a controlled field trial.
The removal of soot in the lubricating sumps of diesel engines is a formidable task, further compounded by the introduction of Exhaust Gas Recirculation (EGR). Efficient removal of soot would help ensure engine durability and engine performance while increasing oil drain intervals thus reducing maintenance costs. This paper describes a method by which soot can be separated from the oil with the application of an electric field by utilizing the small electrical charge on the soot particles. The electric field is applied to a network of electrodes that support an open porous network which stabilizes the weakly bound soot cake. Significantly higher filtration efficiency was achieved as compared to mechanical particulate filtration and centrifugation. The paper also discusses the controlling conditions while detailing the performance testing at both a bench scale level and pilot scale level.
Ash, primarily derived from diesel engine lubricants, accumulates in diesel particulate filters directly affecting the filter's pressure drop sensitivity to soot accumulation, thus impacting regeneration frequency and fuel economy. After approximately 33,000 miles of equivalent on-road aging, ash comprises more than half of the material accumulated in a typical cordierite filter. Ash accumulation reduces the effective filtration area, resulting in higher local soot loads toward the front of the filter. At a typical ash cleaning interval of 150,000 miles, ash more than doubles the filter's pressure drop sensitivity to soot, in addition to raising the pressure drop level itself. In order to evaluate the effects of lubricant-derived ash on DPF pressure drop performance, a novel accelerated ash loading system was employed to generate the ash and load the DPFs under carefully-controlled exhaust conditions. The ash loading system utilized a conventional CJ-4 oil and was coupled to the exhaust of a Cummins ISB diesel engine, allowing for accelerated ash loading and DPF performance evaluation with realistic exhaust conditions. Following DPF performance evaluation, the filters were subjected to a detailed post-mortem analysis in which key ash properties were measured and quantified. Measurements of ash properties and distribution provide key information to interpret the experimental results. In parallel with the experiments, theoretical models were developed and utilized to provide additional details regarding the underlying mechanisms responsible for the manner in which ash alters DPF channel geometry and affects the conditions under which soot is accumulated. The results show a significant increase in local soot loads, elevated filter wall velocities, and a resulting increase in the Peclet number with ash accumulation. Based on the DPF post-mortem analysis and theoretical models, explanations for the differences in DPF pressure drop sensitivity to soot for ash-loaded filters and DPFs containing no ash were developed.
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