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Problems associated with inadequate fuel lubricity were identified in the aeronautical industry in the 1960s, following a succession of in‐flight engine failures. The influence of fuel composition upon fuel lubricity was established, as was the effect of various lubricity additives. Problems associated with inadequate fuel lubricity were also subsequently identified in light‐duty diesel engines when low‐sulphur fuel was introduced. Again, the use of additives or modifications to the refining process overcame the problem at the time, but the continuing trend towards higher injection pressures may require further improvements in current fuel lubricity. The manufacture and use of biodiesel is described, together with the attendant benefits, including use as a lubricity additive in conventional diesel fuel, also disadvantages. The imminent introduction of direct‐injection gasoline passenger car engines has now focused attention on the lubricity of gasoline, which is again likely to become a key issue. Two standardised test procedures for the measurement of fuel lubricities are described.

This paper aims to evaluate the effect of biodiesel additive in fuel system of diesel engines to reduce wear characteristics. Biofuels are environmentally friendly and renewable alternatives to mineral-based fuels and cause low pollution; thus, they can be used to comply with future emission regulations to safeguard environmental and human health.

Two types of diesel fuel, pure petrodiesel and soybean oil, were compared for their fuel properties and tribological performance. The ball-on-disk wear testing method was used as an analytical tool for this purpose. The lubricating efficiency of the fuels was estimated using a photomicroscope to measure the average diameter of the wear scar produced on the test ball.

The wear experiments showed that the wear scar diameters were 1.13 and 0.94 mm for lubrication of the pure petro-diesel and soybean oil, respectively. However, fatty acids containing biodiesel typically have thicker molecular layers than mineral pure petro-diesel, and thus can reduce the wear rate of the sliding metals. This improved the boundary lubrication conditions and the lubricity of the fuel. Biodiesel fuels are effective lubricity enhancers and have greater lubricity enhancing properties than petro-diesel.

The ability of biodiesel to be highly biodegradable and its superior lubricating property when used in compression ignition engines make it an excellent fuel. Biofuel is an attractive alternative fuel to various energy sectors, particularly the transportation sector. Biofuel has immense potential for use in a sustainable energy mixture in the future.

This paper aims to investigate the tribological performance of the decanter cake feedstock biodiesel which was blended in 5 and 10 per cent volume with petroleum diesel.

The tribological performance of the decanter cake biodiesel was tested using the modified ASTM D4172 standard with temperature range from 300°C to 750°C and load range from 392 to 981 N while spindle speed is at 1,200 rpm.

At 5 per cent volume of biodiesel, friction reduced ranging from 10 to 45 per cent at all temperature and load ranges, whereas specific wear rate reduced ranging from 22 to 29 per cent at low load and 4 per cent to 15 per cent at high load for all temperature ranges. Addition up to 10 per cent volume of biodiesel reduced friction ranging from 10 to 35 per cent at all temperature and load ranges, whereas specific wear rate reduced ranging from 15 to 29 per cent only at low load for all temperature ranges.

The standardised test may not represent the actual condition of a real running diesel engine.

Because the lubricity of biodiesel was difficult to determine in a real running engine, this paper provided a standardised test for simplification.

The purpose of this paper was to investigate the lubricity of palm biodiesel (PB)–diesel fuel with plastic pyrolysis oil (PPO) and waste cooking biodiesel (WCB).

Three quaternary fuels were prepared by mechanical stirring. B10 (10% PB in diesel) fuel was blended with 5%, 10% and 15% of both PPO and WCB. The results were compared to B30 (30% PB in diesel) and B10. The lubricity of fuel samples was determined using high-frequency reciprocating rig in accordance with ASTM D6079. The tribological behavior of all fuels was assessed by using scanning electron microscopy on worn steel plates to determine wear scar diameter (WSD) and surface morphology. The reported WSD is the average of the major and minor axis of the wear scar.

The addition of PPO and WCB to B10 had improved its lubricity while lowering wear and friction coefficients. Among the quaternary fuels, B40 showed the greatest reduction in coefficient of friction and WSD, with 7.63% and 44.5%, respectively, when compared to B10. When compared to B30a, the quaternary fuel mixes (B40, B30b and B20) exhibited significant reduction in WSD by 49.66%, 42.84% and 40.24%, respectively. Among the quaternary fuels, B40 exhibited the best overall lubricating performance, which was supported by surface morphology analysis. The evaluation of B40 indicated a reduced adhesive wear and tribo-oxidation, as well as a smoother metal surface, as compared to B20 and B30b.

Incorporation of PPO and WCB in PB–diesel blend as a quaternary fuel blend in diesel engines has not been reported. Only a few researchers looked into the impact of PPO and WCB on the lubricity of the fuel.

Engine component endurance is related to fuel properties. Decreasing the sulfur content of a fuel reduces its lubricity, thus damaging engines and fuel systems. Therefore, promoting the use of a biofuel must involve assessing the functionality and lubricity of the fuel.

The ball-on-ring (BOR) wear tester was applied to determine the optimal additive concentration and the mechanism of reduction of the wear and friction of the diesel engine fuel injection system. The lubricating efficiency of the fuels was estimated by using a photomicroscope to measure the average diameter of the wear scar produced on the test ball. An optical microscope and scanning electronic microscope were used for wear surface examinations.

The wear test revealed that the wear diameter of the steel ball lubricated with either the pure petrodiesel or 20 Wt.per cent Jatropha curcas biodiesel blends was 1.36 or 1.05 mm, respectively. The experimental results indicated that when Jatropha curcas biodiesel was added into petrodiesels to reduce friction, the wear resistance of the fuel blends increased concurrently with increasing Jatropha curcas biodiesel concentration. This was attributed to the presence of stearic acid in Jatropha curcas biodiesel blends. Stearic acid has a strong affinity for metal surfaces; therefore, a chemical coating was formed between the two motion surfaces to protect the two contacted surfaces from wear. Therefore, the proposed Jatropha curcas biodiesel can be used to effectively enhance the lubricity of a petrodiesel under the condition of boundary lubrication.

Using biofuels as the fuels for diesel engines can assist developed and developing countries in reducing the impacts of their fossil fuel consumption on the environment.

The purpose of this paper is to investigate alternatives for four stroke 10w40 motorcycle engine oils. Today, mineral and synthetic‐based lubricants are widely used but because of ecological aspects, which are gaining in importance nowadays and limited resources of mineral oils, environmentally‐friendly biobased lubricants are gaining in importance. Biobased lubricants are also important for using national resources rather than importing crude oils which are limited. The main consumption of lubricant market is motor oils. In this study, starting from mineral, synthetic and biobased lubricants; mineral, synthetic, biomineral and biosynthetic based four stroke motorcycle engine oils (10w40) are prepared, then lubricity properties of the motor oils are determined.

The lubricity tests of the samples are done in a fixed forced lubricity test rig and the motorcycle motor oil preparation are conducted according to ASTM test methods.

The results show that 5 per cent of biobased lubricants will be suitable for preparing 10w40 motor oils in both mineral and synthetic based motor oils. Also improvements in the lubricity properties with the blend with biobased lubricants are seen.

The paper presents biomineral and biosynthetic 10w40 motor oils as alternative candidates for motorcycle motor oils.

Examines the issues surrounding fuel lubricity by explaining the background to the problems surrounding lubricity in diesel engines. As the need for low sulphur diesels arose it became clear that a universally accepted bench test was required and ISO working group SC7/WG6 was set up in 1992 to decide on a standard test. The group recommended that an HFRR (high frequency reciprocating rig) ball‐on‐flat test should be adopted. Describes the test methodology.

This paper aims to investigate the tribological properties of two protic ionic liquids used as lubricity-improving additives in the water. Their concentration was optimized for different metal friction pairs including bearing steel, stainless steel and aluminum alloy.

In this study tribological properties were investigated by using a ball-on-plate reciprocating tribometer. Three different friction pairs were selected: bearing steel-bearing steel; bearing steel-stainless steel; bearing steel-aluminum alloy. To optimize the concentration of investigated protic ionic liquids four concentrations were selected. Wettability was investigated using the droplet method. The corrosiveness of additive-loaded water was investigated using the iron chip method.

The results show that by using protic ionic liquids the lubricity of water could be greatly improved. However, the friction pair material and additive concentration play a significant role. The positive tribological effect was attributed to the polarity of the additive molecule which tends to form an adsorption layer. The polarity of molecules also leads to better surface wettability. It was also found that both investigated protic ionic liquids can improve the anticorrosion properties of water.

To the best of the authors’ knowledge, this is the first study to present a complex investigation of tribological properties of two protic ionic liquids as additives in the water. In this case, three different metal friction pairs and four additive concentrations were investigated. The results could be interesting to those who are working in the field of water-based lubricants and luck for multipurpose lubricity-improving additives.

A large number of diesel engine failures have been reported in the immediate past. The large proportion of these engines that were investigated, were recently overhauled engines that failed soon after the overhaul process. In some cases, these engines failed on the dynamometer, while it was tested before delivery to the customer. The most common failure on a large number of these engines, were pistons seizing in the crown region causing seizure of the piston in the cylinder. Tests were done to correlate the lubricity of the fuel that was used and the failure of the engines. Limits were obtained from which it could be determined when the fuel was not of a proper quality and where engine failures took place. It is finally recommended that the specification SABS 342 be amended to include the requirements for the lubricity of diesel fuels.