Abstract
By now, the oxidative degradation of lubricating oils for thermal engines was exclusively charged to the tough working conditions (high pressures and temperatures, catalytic action of metal traces) from the engines. The paper proves that oxidative degradation of oil occurs even under normal pressure and temperature conditions, only under the influence of vibrations. Using UV-VIS spectroscopy, the worsening of oil quality, mainly the acid content, is evidenced and explained.