BlueEFFICIENCY is branding used by Mercedes-Benz for cars using optimised engineering of various systems for reduced emissions and improved fuel consumption. Over the years BlueEFFICIENCY has expanded into an entire R&D ethos and now relates to everything from improved aerodynamics to systems like start/stop and advanced alternators that can ‘harvest’ energy when the car is slowing or even ‘decouple’ to reduce the load on the engine when the battery is charged.
Previously BlueEFFICIENCY models were sold as standalone variants prioritising low CO2 emissions and improved fuel economy but it has since expanded across entire ranges and you will encounter the branding on many Mercedes-Benz cars that prioritise efficiency.