MERCEDES-BENZ has tweaked the turbodiesel inline fours of the C220 CDI and E250 CDI, improving fuel economy while leaving power and torque intact.
Fuel economy for the C220 CDI is reduced to 4.5 l/100km, while the E250 CDI consumes 4.9 l/100km. That represents a 1.8 l/100km drop for the C-Class and a 1.1 l/100km reduction for the E-Class.
Marketed under Benz's eco-friendly BlueEfficiency badge, power output remains at 125kW for the C220 CDI and 150kW for the E250 CDI. Torque is unchanged at 400Nm and 500Nm respectively.
Most of the fuel economy savings come from the adoption of an automatic start-stop system, which saves fuel by shutting down the engine when the vehicle is stopped.
Further refinements, such as a lighter crankshaft, variable-output oil pump and on-demand ancillaries, improve efficiency by imposing less drag on the engine, thus wasting less fuel.
The E250 CDI's engine is coupled to a seven-speed automatic, which boasts greater efficiency than the five-speed unit fitted to current Australian-delivered models.
The gearbox has undergone some changes to adapt it to the start-stop system, with the biggest addition being an electric oil pump that keeps the hydraulics pressurised when the engine is off.
A taller differential ratio also boosts efficiency.
Both models are slated to go on sale in Europe in the third quarter of this year, and Mercedes-Benz says there will be more BlueEfficiency models to come.
An Australian release has yet to be be confirmed, while European pricing will be announced later this year.