The aim for cleaner and more efficient energy from the internal combustion engines makes necessary to ensure the conditions for the exploitation of alternative fuels. The vibrations on engines are primarily understood as effects of mechanical failures, but the engine vibration is subject of the fuel combustion effects too. This effects will depend on the fuel type and its capacity to be burned. The vibrations of a diesel engine were measured and analyzed with a frequency spectrum calculated with Fast Fourier Transforms. The engine was operated with a fuel blend from 10 % recycled lubricating oil with 90% diesel as well as only diesel. It was found the engine operation with this fuel blend has a lower vibration level in comparison with the use of pure diesel. The goal of this research is to determine the properties of the fuel blend, which provides more stability to the engine by means of vibrations reduction. The fuel properties that influences the engine stability are the flash point, the cetane number and the heat value. The improvements of these properties, allows to keep the engine performance with better stability during its operation at different speeds. The testing of the engine performance by means of the vibrations analysis is a powerful tool to determine the engine’s behavior from the functional and endurance point of view. The vibrations measurements of the diesel with the use of different fuels types and properties makes possible to choose and identify the fuel properties that bring more stability to the engine.