Both cars are powered by Mercedes-Benz's 2.2-litre four-cylinder turbo-diesel engine, though power outputs vary between models with the C220 CDI scoring a 127kW/399Nm and the E250 CDI gaining a 152kW/500Nm offering.
The engines have been revised for even greater efficiency with improvements that include a reduced mass crankshaft (by cutting the number of counterweights from eight to four), better oil pressure regulation and revised turbocharged that reduces parasitic loss.
Both models also get an automatic start-stop system for the first time with a seven-speed automatic transmission.
As you'd expect, fuel efficiency is also very impressed with the C220 CDI achieving a combined figure of 4.51L/100 and the E250 CDI 4.91L/100km. CO2 figures are 119g/km and 129g.km respectively.
The two new Mercedes-Benz variants will go on sale in Europe from Q2.