In this research project, we analyze the effects of the introduction of car stocks on logistics costs in the current service process of Royal Philips. A new service process is proposed, that includes spare parts inventory holding at the cars of Field Service Engineers (FSEs). The main cost buckets that cause the change in logistics costs at the introduction of car stocks compared to the current service process are defined. Logistics costs are defined as all costs related to spare part handling, inventory holding, spare part transportation, and FSEs. We develop a cost model to determine the costs for the defined cost buckets for both the current and proposed service process, under given basestock levels for the car stocks. An optimization algorithm is developed to, given the car size of the FSE, obtain close-to-optimal basestock levels that minimize total logistics costs, with corresponding car stock review period length and number of needed fulltime FSEs.