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The commonly accepted interlayer shear mechanism for layered materials as oil additives remains a challenge with the emergence of two-dimensional materials. In this work, the lubrication effectiveness of MoS 2 and BN nanosheets with a similar size was investigated as oil additives using block-on-ring tests. BN nanosheets reveal remarkable anti-wear performance and a reduction of wear depth of about 50%, whereas, the expected friction and wear reduction were not found for MoS 2 nanosheets. X-ray photoelectron spectroscopy (XPS) investigation indicates the generation of boron-based tribofilm for BN nanosheets and MoS 2 -complex tribofilm for MoS 2 nanosheets. Together with the thermal stability analysis, we found that it is the high strength tribofilm with high oxidation resistance, but not the layer structure, that plays a critical role in lubrication enhancement. This study highlights the advance of 'depositing tribofilm' mechanism in novel additive design. Image 1 • Layered materials with similar size and shape were selected. • Expected friction and wear reduction was not found for MoS 2 nanosheets in this study. • BN nanosheets reveal the remarkable anti-wear property with strong tribofilm strength. • It is a challenge to explain the results by using interlayer shear mechanism. • Depositing tribofilm mechanism would be preferable for novel particle additive design. [ABSTRACT FROM AUTHOR]