Nissan X-Trail 2023 Owners Manual
7.8.3. ECO mode
Assists the driver's ECO-driving. The engine and transmission points are adjusted for improved fuel economy, providing such driving features as smooth starting or constant cruising.

Selecting the [ECO] mode will not necessarily improve fuel economy as many driving factors influence its effectiveness.
It is recommended to select other than [ECO] mode when acceleration is required such as when:
driving with a heavy load of passengers or cargo in the vehicle
driving on a steep uphill slope
Owners Manual