Search Results

To comply with increasingly strict emission regulations, diesel vehicles are equipped with Diesel Particulate Filters (DPF) to capture fine particulate matter (PM) from exhaust gas. However, due to the limited capacity of DPF to capture soot, periodic regeneration processing is required to burn it off. The ash created by metal-based additives in engine oil accumulates in DPF, leading to issues such as increased regeneration frequency and decreased fuel efficiency. To solve this problem, researchers have developed diesel engine oil with reduced ash content. However, the authors are taking it a step further and developing a diesel engine oil without metal-based detergents and anti-wear additives, for even more significant environmental impact reduction. This paper describes the development of an ashless engine oil with DH-2 performance, the effects of the developed engine oil on DPF, and the results of engine and actual field tests.

Diamond-Like Carbon (DLC) is a promising engine material for reducing friction and wear on sliding parts. By contrast, MoDTC lubricant additives are known to promote the wear of a-C:H films. However, the mechanism that promotes wear and the formation of tribofilms on DLC parts when in contact with molybdenum-based lubricant additives has not been sufficiently studied. The purpose of this research is to determine the wear promotion mechanism and formation of tribofilm on DLC by lubricant additives by comparing friction and wear properties. We conducted friction and wear tests using a tribometer with DLC (ta-C, ta-C:H, a-C, and a-C:H) blocks, FC250 (cast iron) rings, and oils containing lubricant additives (MoDTC, MoDTP, and Mo without DTC ligand) by observing and analyzing the sliding surfaces of specimens. No wear was observed for any of the DLCs (ta-C, ta-C:H, a-C:H, and a-C) in combination with oils containing MoDTP or Mo without DTC ligands.

The deposition of ash derived from engine oil on the surface of diesel particle filters (DPF) has recently been reported to degrade the performance of the DPF. It is generally known that phosphorus in engine oil is adsorbed on the surface of an automotive exhaust catalyst, reducing the performance of the catalyst. Thus, the amounts of ash and phosphorus in engine oil have been decreased. We have developed a non-phosphorus, non-ash engine oil (NPNA) that does not contain metal-based detergents or zinc dialkyldithiophosphate (ZnDTP). Various engine tests were performed, and we confirmed that under normal running conditions, the NPNA oil had a sufficiently high piston detergency and wear resistance-two important requirements for engine oil-to meet current American and Japanese standards. However, the piston detergency of NPNA required further improvement when engine running conditions were more severe.

At present, the lifetime of engine oil is judged by chemically measuring the changes in its properties while running of an actual vehicle or by setting the standards for its replacement cycle in terms of travel distance and time. The advantage of the former is that the lifetime can be judged with a high degree of reliability, but its disadvantage is that information on the lifetime is difficult for users to obtain. The problem with the latter is that the standards are unreliable. Therefore, users need a simple and reliable method to evaluate the degradation of engine oil so they can determine the appropriate time to change it. We examined the possibility of evaluating the lifetime of engine oil by measuring its capacitance using a comb-shaped electrode. As a result, we found that the capacitance of four types of engine oil collected at markets tended to decrease during the initial stage of degradation and then increased in the later stage.

Recently, deposition of ash derived from engine oil on the surface of a diesel particle filter (DPF) has been reported to worsen the performance of the DPF. It is generally known that phosphorus in engine oil is adsorbed on the surface of an automotive exhaust catalyst and reduces the performance of the catalyst. Thus, the amounts of ash and phosphorus in engine oil have been decreased. We have developed a non-phosphorus and non-ash engine oil (NPNA) that does not contain metal-based detergents and zinc dialkyldithiophosphate (ZnDTP). We performed a performance test for NPNA using an actual engine and reported that the piston detergency and anti-wear performance of NPNA were sufficiently high. However, the piston detergency of NPNA required further improvement when engine running conditions were more severe.

To explore the measures that can be used to improve the fuel economy of internal combustion engines, we investigated how friction at the piston ring-cylinder liner interface is influenced by the boundary lubrication performance of engine oils. We formulated several engine oils with varying boundary lubrication performance and tested them for ring-liner friction by using a floating liner friction tester. We used friction modifiers (FMs) to modify the boundary lubrication performance of engine oils. We found that ring-liner friction is well correlated with the friction coefficients in boundary lubrication regimes when measured by a laboratory friction tester. We also found that the impact of the boundary lubrication performance of engine oils was emphasized in low viscosity engine oils. It makes it possible for improved boundary lubrication performance to inhibit or overcome the viscosity reduction-induced increase of friction energy.

Automobile exhaust gas contains various harmful substances other than carbon dioxide, so exhaust gas post-processing devices have been developed to reduce their environmental load. Engine oil has contributed to the improvement of automobiles' environmental performance due to its excellent fuel-saving and long-drain properties. Recently, the lifetime of an exhaust gas post-processing device has been reported to decrease due to ash and phosphorus in engine oil. We have developed non-phosphorus and non-ash engine oil (NPNA), in which metal-based detergents and zinc dialkyldithiophosphate (ZnDTP) were not contained. We have performed a verification test for NPNA using an actual engine. In a performance test for a diesel particulate filter (DPF), the amount of soot and ash deposited onto a DPF was smaller when NPNA was used than when commercially available engine oil was used.

Engine oils normally contain calcium detergents and ZnDTPs to have detergency and antiwear performance. However, it has been recently understood that these additives could deteriorate filter performance in catalyst and DPF. In this background this paper explains the study and the development about new type of engine oil excluding metal detergents and phosphorus compounds. The developed engine oil shows good durability in several JASO engine tests and a fleet test by formulating newly developed additives as substitute for calcium detergents and ZnDTPs.

As well as a four-wheeled vehicle, in the field of motorcycle, development of the CO2 reduction technology and practical use are required for global environment. Zinc dialkyldithiophosphate (Zn-DTP) type additives are widely used for engine oil formulations. However, phosphorus compounds are environmental load materials. The reduction of the quantity of phosphorus compounds in engine oils is required to reduce poisoning of three-way catalysts used to purify exhaust gases from internal combustion engines. Ito1) reported that they developed a sulfur-based additive as a substitute for Zn-DTP. Their non-phosphorus engine oil formulation for four-wheeled vehicles with a sulfur-based additive was examined to evaluate its anti-wear performance using the following test methods: JASO M328 for gasoline engines (KA24E) and JASO M354 for Diesel engine (4D34T4).

Just as CO2 reduction is required of four wheeled vehicles for environmental protection, similar environmental concerns drive the development of motorcycle oil technology. Zinc dialkyldithiophosphate (Zn-DTP) type additives are widely used for engine oil formulations. However, phosphorus compounds are environmental load materials. The reduction of the quantity of phosphorus compounds in engine oils is required to reduce poisoning of three-way catalysts used to purify exhaust gases from internal combustion engines. Mr. Ito and his co-authors1) reported that they developed a sulfur-based additive as a substitute for Zn-DTP. Their non-phosphorus engine oil formulation for four-wheeled vehicles with a sulfur-based additive was examined to evaluate its anti-wear performance using the following test methods:JASO M328 for gasoline engines (KA24E) and JASO M354 for Diesel engine (4D34T4).

Energy conserving performance by engine oils is required even for motorcycles from the viewpoint of environmental issues. The fuel efficiency of passenger car engine oils has been improved through lower viscosity and usage of friction modifiers. However, engine oils containing friction modifiers such as Mo compounds may not be applied to four-stroke motorcycles, because motorcycles normally have a wet clutch system inside the crankcase and such engine oils can decrease the clutch capacity. Therefore, it is important to investigate the effects of oil formulation in order to develop motorcycle engine oils, which can improve fuel efficiency and preserve clutch capacity1)∼2). In this study, fuel efficiency of prototype oils was evaluated with a motorcycle engine motoring tester. In addition, friction coefficients of engine oils formulated with different additives such as dispersants and detergents in clutch system were evaluated with an SAE No. 2 clutch friction tester.

The energy conserving by engine oils has been required from the viewpoint of the environmental issue. The fuel efficiency of passenger car engine oils has been improved by adding friction modifiers. However, engine oils containing friction modifiers can not be applied to 4-stroke motorcycles. Because motorcycles normally have a wet clutch system inside the crankcase and such engine oils can decrease the clutch capacity.1) ∼ 2) Therefore, it is important for motorcycle engines to investigate additives, which can increase friction coefficient on paper-based friction materials. In this study, friction coefficients of engine oils formulated with different additives such as dispersants and detergents were evaluated with a reciprocating friction tester. Several types of polybutenyl succinimides, sulfonates, phenates and salicylates were used as dispersants and detergents.