This paper aims to show the design and construction of a used oil rapid test kit. The kit allows evaluating used oil degradation and contamination by crepitation, oil blot, viscosity and particle content test. It consists of four units: oil blot maker, heating plate, falling ball viscometer and ferrous particle detector. The main contribution of the work are the devices and methods developed to accurately measure both the viscometer ball falling time and to detect wear ferromagnetic particles. The kit has produced satisfactory results compared to those obtained in laboratory tests.