Although the implications of increasingly automated road transport for driver behavior are often studied from the perspective of safety and comfort, automation is also expected to increase energy efficiency and thus contribute to environmental sustainability. However, drivers’ interaction with automated systems that optimize the vehicle’s energy efficiency by controlling the energy flows has not yet been well understood. Based on the perspective of user-energy interaction, the present research constitutes a first case study in this respect, focusing on hybrid electric vehicle (HEV) drivers. Results from an online questionnaire study with 121 HEV drivers indicated high user diversity in the interaction with the eco-automation, ranging from complete reliance to active disengagement of eco-automation. These interaction patterns were significantly related to differences in fuel efficiency, as well as the drivers perceived trust and knowledge of the eco-automation. The study provides evidence for the relevance of understanding drivers’ interaction with eco-automation to ensure the sustainability of future road transport.