The subject of the disclosure concerns microcapsules including a core containing one or more alkali metal borates, optionally hydrated, dispersed in one or more lubricating base oils of mineral, synthetic or natural origin, and a polymer shell. Another subject of the disclosure is a lubricating oil including microcapsules. A further subject of the disclosure is the use of microcapsules according to the disclosure as anti-wear and/or extreme pressure additive for lubricant compositions. A further subject of the disclosure is a method for preparing microcapsules by interface polymerization.