A cooling device comprising a cooling circuit, the cooling circuit comprising: a compressor, which is adapted to compress cooling agent present in the cooling circuit during an active cooling mode, wherein the compressed cooling agent contains lubricant oil from the compressor; a condensing unit, which is connected to the compressor by a first fluid line of the cooling circuit; an evaporating unit, which is connected to the condensing unit by a second fluid line of the cooling circuit; an expansion device, which is arranged in the second fluid line; an additional evaporator (135, 147, 159), which is connected to the evaporating unit by a third fluid line of the cooling circuit, and which is connected to the compressor by a fourth fluid line of the cooling circuit, the cooling device being configured so that during the active cooling mode lubricant oil is adapted to be transferred from the compressor through the condensing unit, through the expansion device, through the evaporating unit, through the additional evaporator (135, 147, 159) and through the fourth fluid line back to the compressor; a first fluid by-pass line, which connects the condensing unit with the evaporating unit; and a second fluid by-pass line, which connects the evaporating unit with the condensing unit, wherein the first fluid by-pass line comprises a first by-pass valve and wherein the second fluid by-pass line comprises a second by-pass valve, which are adapted to close the first fluid by-pass line and the second fluid by-pass line in the active cooling mode, respectively, wherein the cooling device further comprises a control, the cooling device being characterised in that the third fluid line or the additional evaporator (135, 147, 159) comprises a first sensor arrangement, which is adapted to detect a superheat of the cooling agent flowing through the third fluid line or through the additional evaporator (135, 147, 159), and in that the control is adapted to operate the expansion device and/or the first by-pass valve in dependence of the detected superheat of the cooling agent. a compressor, which is adapted to compress cooling agent present in the cooling circuit during an active cooling mode, wherein the compressed cooling agent contains lubricant oil from the compressor; a condensing unit, which is connected to the compressor by a first fluid line of the cooling circuit; an evaporating unit, which is connected to the condensing unit by a second fluid line of the cooling circuit; an expansion device, which is arranged in the second fluid line; an additional evaporator (135, 147, 159), which is connected to the evaporating unit by a third fluid line of the cooling circuit, and which is connected to the compressor by a fourth fluid line of the cooling circuit, the cooling device being configured so that during the active cooling mode lubricant oil is adapted to be transferred from the compressor through the condensing unit, through the expansion device, through the evaporating unit, through the additional evaporator (135, 147, 159) and through the fourth fluid line back to the compressor; a first fluid by-pass line, which connects the condensing unit with the evaporating unit; and a second fluid by-pass line, which connects the evaporating unit with the condensing unit, wherein the first fluid by-pass line comprises a first by-pass valve and wherein the second fluid by-pass line comprises a second by-pass valve, which are adapted to close the first fluid by-pass line and the second fluid by-pass line in the active cooling mode, respectively, wherein the cooling device further comprises a control, the cooling device being characterised in that the third fluid line or the additional evaporator (135, 147, 159) comprises a first sensor arrangement, which is adapted to detect a superheat of the cooling agent flowing through the third fluid line or through the additional evaporator (135, 147, 159), and in that the control is adapted to operate the expansion device and/or the first by-pass valve in dependence of the detected superheat of the cooling agent.