The oil quality in an oil reservoir of a pump is monitored using the disclosed oil-monitoring sensor. The oil-monitoring sensor includes a first capacitive portion for measuring oil level and a second capacitive portion for measuring dielectric constant of the oil. Changes in dielectric constant of the oil are indicative of degradation of the quality of the oil (e.g., due to contaminants, oxidation, etc.) So oil-monitoring sensor is used to indicate various parameters about the oil quality to an operator. Using the disclosed sensors, the quality of the lubricant and/or cooling oil used by the pump may be monitored without needing to be present at the pump, or without needing to access the interior of the pump (or oil reservoir).