A lubrication device comprising: a lubricant feed circuit; a bypass circuit; and a valve interposed between the feed circuit and the bypass circuit and comprising: an inlet connected to said feed circuit; a first outlet suitable for being connected to elements to be lubricated; a second outlet connected to the bypass circuit; a valve member housed in a cavity of the valve and separating a first chamber from a second chamber, said first chamber being connected to the inlet, said valve member being suitable for sliding between a first position and a second position, and presenting, beside the first chamber, a hydraulic actuation surface for urging it towards the second position, and, beside the second chamber, a hydraulic actuation surface for urging it towards the first position; and an actuator for returning the valve member towards the first position; and wherein in said first position, a fluid flow passage from the first chamber to the second outlet is open, while a fluid flow passage from the first chamber to the first outlet is closed; and in the second position, the fluid flow passage from the first chamber to the first outlet is open, while the fluid flow passage from the first chamber to the second outlet is closed; the lubrication device being characterized in that, at least in the second position, the valve member separates said first and second chambers (16, 17) in substantially leaktight manner, while the second chamber remains in fluid flow communication with the second outlet. a lubricant feed circuit; a bypass circuit; and a valve interposed between the feed circuit and the bypass circuit and comprising: an inlet connected to said feed circuit; a first outlet suitable for being connected to elements to be lubricated; a second outlet connected to the bypass circuit; a valve member housed in a cavity of the valve and separating a first chamber from a second chamber, said first chamber being connected to the inlet, said valve member being suitable for sliding between a first position and a second position, and presenting, beside the first chamber, a hydraulic actuation surface for urging it towards the second position, and, beside the second chamber, a hydraulic actuation surface for urging it towards the first position; and an actuator for returning the valve member towards the first position; and wherein an inlet connected to said feed circuit; a first outlet suitable for being connected to elements to be lubricated; a second outlet connected to the bypass circuit; a valve member housed in a cavity of the valve and separating a first chamber from a second chamber, said first chamber being connected to the inlet, said valve member being suitable for sliding between a first position and a second position, and presenting, beside the first chamber, a hydraulic actuation surface for urging it towards the second position, and, beside the second chamber, a hydraulic actuation surface for urging it towards the first position; and an actuator for returning the valve member towards the first position; and wherein in said first position, a fluid flow passage from the first chamber to the second outlet is open, while a fluid flow passage from the first chamber to the first outlet is closed; and in the second position, the fluid flow passage from the first chamber to the first outlet is open, while the fluid flow passage from the first chamber to the second outlet is closed; the lubrication device being characterized in that, at least in the second position, the valve member separates said first and second chambers (16, 17) in substantially leaktight manner, while the second chamber remains in fluid flow communication with the second outlet.