Friction and wear behaviour of different concentrations of hex-boron nitride (h-BN) nanoparticles in engine oil of grade SAE 20W50 were studied at various loads. These tribological studies were conducted using a four-ball wear test machine and a pin-on-disc universal tribometer. Anti-wear properties of SAE 20W50 + h-BN were studied on the four-ball wear test machine as per ASTM D4172 standard. Friction and wear properties of SAE 20W50 + h-BN on piston ring and cylinder liner tribo-pair were studied using the universal tribometer. Nanoparticles of h-BN mixed in lubricant showed excellent tribological performance. In most of the cases, h-BN nanoparticles as additive reduced the wear loss by 30-70% at various loads. The minimum value of coefficient of friction (0.0401) was found with SAE 20W50 + 3 wt% of h-BN at normal load of 100 N. Scanning electron microscopy and Raman spectroscopy were used for characterisation of h-BN and wear scars.

Automotive manufacturers made significant efforts to achieve an overall increase in the energy efficiency and to reduce the toxic emission level. In the way to achieve these goals, non-conventional engine technologies were brought to the market with improved efficiency and controlled emission system. Numerous other supporting technologies which include biofuels and newly improved lubricants were also involved to contribute in automotive engine system improvement. The problem of friction and wear being inbred to the automotive application, further raise environmental hazards by way of more fuel consumption and wear debris. For several years there have been numerous efforts to reduce the amount of fuel consumed by automotive engines. Many of the solutions been strictly mechanical based. Other efforts have revolved around finding the lubricants that reduce the overall friction in the engine. Lubricants perform an anti-friction media which facilitate smooth operation, reduce friction, wear and risk of frequent failure. Due to this ever-increasing demand for lubricant, a considerable amount of work has been done to modify the lubricating oils with additives to enhance their overall properties. This review paper is aimed to highlight the research carried out in the field of lubricating oil with nano additives for the automotive applications.

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Nanolubrication is one of the recent innovative technologies used in lubrication science. It involves dispersion of various types of nanoparticles in different concentrations in the conventional lubricant and studies the tribological properties of these lubricants on a particular tribopair under different operating parameters. Nanoparticles can be considered as potential lubricant additives. They present several major advantages compared to organic molecules currently used as lubricant additives, which include their nanometre size allowing them to enter the contact area easily. The real contact area is decreased when nanoparticles are entrapped between the mating surfaces. They are often efficient at ambient temperature. Thus, no induction period is necessary to obtain interesting tribological properties. Further, nanoadditives also improve the thermo-physical properties of the lubricant. A comprehensive review is provided with the aim to analyse and explore tribological and thermo-physical properties of nanolubricants on various tribopairs used for engineering applications. Recent advancements like hybrid nanofluids and biolubrication are also discussed that further provides the solutions for sustainable lubrication.

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