To suppress CO₂ emissions through policies and technology development, eco-driving techniques are required to be actively practiced as an effective method to improve fuel efficiency. Among the methods to practice eco-driving, the active eco-mode is a function that changes the driving mode of a vehicle by the driver’s choice. This study aims to analyze the effect of driving modes (normal-mode, eco-mode) on CO₂ emissions through on-road tests under different driving conditions. The eco-mode activation under normal temperature conditions emitted relatively less CO₂ emissions than the normal-mode driving. Under high-temperature conditions, fuel economy deteriorated since an additional load was required for heating, ventilating, and air conditioning (HVAC) system operation. However, when using the eco-mode, the control of the HVAC system was integrated with the effect of powertrain logic, which achieved a higher reduction rate of CO₂ emissions than the normal temperature condition. In particular, the impact of reducing fuel consumption was confirmed in the urban section with many stops and departures, which is determined to result from a combination of gear shifting and acceleration pedal filtering strategies. Meanwhile, the eco-mode logic has not been applied much in rural and motorway sections.