A recent trend in the automotive industry is related to the switch of more and more customers towards vehicles’ rental, rather than ownership. According to this, the car-sharing sector is rapidly expanding, favoured also by the circular economy wave, as well as by complementary factors (wide internet access, advanced level of IT, good customer acceptance). Car-sharing can be classified as a product-service system (PSS), i.e., a bundle of a product (in this case the car) and a service (the rental). To assess the quality of a PSS no standard methodologies are diffused. Recent studies apply Topic Modelling algorithms to the users’ reviews to grasp the quality determinants, represented by the discussion topics.