The purpose of this article is to advance empirical sustainability-evaluations of carsharing-systems. Carsharing, a frequently cited example of a product–service system (PSS), is currently morphing from a niche into a mainstream mode of transportation. Carsharing has the potential to provide a more sustainable mobility-option compared to private car usage, for example by reducing the overall motor-vehicle traffic in cities. However, the quantification of this potential is complex, and few studies have analyzed the fundamental impacts of the chosen measurement-methodology on the results of empirical carsharing-evaluations. This article analyses the time- and method-interdependencies of carsharing-studies based on a generic model structuring the adaptation of the mobility-behavior of carsharing-users over time. A paradigm shift from a static to a dynamic view on impacts of the PSS carsharing is proposed, which could support policymakers enacting carsharing-regulations in cities. The analysis of generic methodological interdependencies when conceptualizing impacts as dynamic processes is generalizable to impact-assessments of new technologies changing user-behavior over time.