A method of measuring lubricant level and quality using a lubricant sensor, the lubricant sensor comprising a plurality of electrodes (110, 120, 130), and the method comprising: placing the lubricant sensor into a lubricant; providing a first current, which is AC at a first frequency, between electrodes of the lubricant sensor; measuring, at the first current, a capacitance parameter representative of the capacitance between the electrodes between which the first current is provided; determining the level of the lubricant in which the sensor is placed from the measured capacitance parameter; providing a second current between electrodes of the sensor, the second current being provided at a different time to the first current and being either: i) DC; or ii) AC at a second frequency which is lower than the first frequency; measuring, at the second current, an impedance or resistance parameter representative of the impedance or resistance between the electrodes between which the second current is provided; and determining the quality of the lubricant in which the sensor is placed from the measured impedance or resistance parameter; wherein the lubricant sensor comprises a first electrode, a second electrode, and a third electrode; the first current is provided between the first electrode and the second electrode, and between the first electrode and the third electrode; the capacitance parameter is measured, at the first current, between the first and second electrodes and between the first and third electrodes and used to determine the capacitance between the first and second electrodes and between the first and third electrodes; the level of the lubricant in which the sensor is placed is determined by comparing the capacitance between the first and second electrodes with the capacitance between the first and third electrodes; the second current is provided between the first electrode and one of the second and third electrodes (120, 130); and the impedance or resistance parameter is measured at the second current between the first electrode and said one of the second or third electrode. placing the lubricant sensor into a lubricant; providing a first current, which is AC at a first frequency, between electrodes of the lubricant sensor; measuring, at the first current, a capacitance parameter representative of the capacitance between the electrodes between which the first current is provided; determining the level of the lubricant in which the sensor is placed from the measured capacitance parameter; providing a second current between electrodes of the sensor, the second current being provided at a different time to the first current and being either: i) DC; or ii) AC at a second frequency which is lower than the first frequency; measuring, at the second current, an impedance or resistance parameter representative of the impedance or resistance between the electrodes between which the second current is provided; and determining the quality of the lubricant in which the sensor is placed from the measured impedance or resistance parameter; wherein the lubricant sensor comprises a first electrode, a second electrode, and a third electrode; the first current is provided between the first electrode and the second electrode, and between the first electrode and the third electrode; the capacitance parameter is measured, at the first current, between the first and second electrodes and between the first and third electrodes and used to determine the capacitance between the first and second electrodes and between the first and third electrodes; the level of the lubricant in which the sensor is placed is determined by comparing the capacitance between the first and second electrodes with the capacitance between the first and third electrodes; the second current is provided between the first electrode and one of the second and third electrodes (120, 130); and the impedance or resistance parameter is measured at the second current between the first electrode and said one of the second or third electrode.