A new method has been developed for measuring the oil films on cylinder walls in engines that offers benefits in improved understanding of oil transport and consumption. The unique aspect of this work is that fiber optics and laser induced fluorescence are combined to measure the oil film thickness. As a result the system is much less intrusive than previous methods using windows to observe the fluorescence.Static tests were used to demonstrate the characteristics of the technique. Dynamic tests, performed on a Cameron Plint wear tester, showed the capability of the system to measure thin films under dynamic conditions and at high loads and temperatures. Finally, the system was installed in a diesel engine and used to measure oil film thicknesses under fired conditions.