The formation of thermal lenses in a volume of motor oil was investigated by a holographic method. The beam shape of incident laser light expands after passing through a liquid medium and it is a well-known photo-thermal phenomenon or “the thermal lens effect” [1-2]. The formation of thermal lenses in a volume of motor oil was investigated by a holographic method. At the beginning the hologram of cuvette with the motor oil was recorded using the laser radiation of 532 nm. Then the sample was illuminated by a focused laser beam 447 nm and the formation of a thermal lens was observed by the phase changing of the object beam. Also, laser irradiation 447 nm excites the luminescence of motor oil. To investigate the luminescence spectra of oil the hologram of the object can be used as a diffraction grating. For this purpose, in the optical scheme was added a narrow vertical slit without changing the position of the other elements of the optical scheme. The luminescence spectrum is recorded on the matrix of digital camera and after computer processing of the image the spectral distribution of the luminescence signal can be obtained.