This research investigates the energy savings achieved through eco-driving controls in connected and automated vehicles (CAVs), with a specific focus on the influence of powertrain characteristics. Eco-driving strategies have emerged as a promising approach to enhance efficiency and reduce environmental impact in CAVs. However, uncertainty remains about how the optimal strategy developed for a specific CAV applies to CAVs with different powertrain technologies, particularly concerning energy aspects. To address this gap, on-track demonstrations were conducted using a Chrysler Pacifica CAV equipped with an internal combustion engine (ICE), advanced sensors, and vehicle-to-infrastructure (V2I) communication systems, compared with another CAV, a previously studied Chevrolet Bolt electric vehicle (EV) equipped with an electric motor and battery. The implemented control is a universal speed planner that solves the eco-driving optimal-control problem within a receding-horizon framework, utilizing V2I communications for signal phase and timing information. The controller calculates accelerator and brake pedal positions using the vehicle’s state and real-time environmental information. Both the Pacifica, target vehicle, and the Bolt, EV, are equipped with a drive-by-wire system. The experiments encompass five road scenarios repeated three times, covering a 3.7-km track with various stop signs, traffic signals, and speed limits. Three control calibrations are employed to represent human-driver-like, non-connected automated, and V2I-connected driving. First and foremost, the results demonstrate functional eco-driving controls with no extreme acceleration or traffic law violations in the Pacifica (ICE vehicle). Energy savings of up to 6% without connectivity and up to 22% with V2I connectivity are achieved in the ICE vehicle as well. Additionally, a comparison is made between an ICE vehicle and an EV to analyze the energy-saving impacts of eco-driving controls across different powertrain characteristics. In conclusion, this study emphasizes the significance of correlating powertrain design with controls and eco-driving strategies during the development of CAVs.