Steel pistons cut fuel consumption by 3%

As part of its quest for ever greater fuel economy, Mercedes-Benz has replaced the aluminium pistons in its diesel passenger cars with hi-tech steel ones.

The automotive giant says the swap will enable fuel savings of around 3% and also help to reduce CO2 emissions. The steel pistons will debut in the V6 diesel engine of the Mercedes-Benz E 350 BlueTEC, within an aluminium crankcase. With the new pistons in place, Mercedes says the car will deliver the same engine output (190kW/258hp), yet only use around 5 litres of diesel fuel per 100km. Because steel has a lower level of thermal conductivity compared to aluminium, higher temperatures can be reached within the combustion chamber. This in turn leads to increased ignition quality and reduced combustion duration. The overall result is lower fuel consumption and CO2 emissions. "The higher strength of the steel also allows for a more compact piston design, which more or less compensates for the fact that the material is around three times as dense," said Mercedes in a statement. "The innovative steel pistons are as much as 13mm lower than the aluminium equivalents used until now."