Mercedes has suggested the engine will later be made available with different outputs, and though powertrain lead engineer Karsten Krebs would not be drawn on a realistic maximum power figure for the four-pot, he did tell Autocar that the three initial tunes are “where we start”, suggesting there is the possibility for uptuned sporting derivatives in the future.
Mercedes is still homologating the engine ahead of the CLA’s launch next year, and has not yet given any projected MPG figures, but when asked for a hint, Krebs said “we feel you’re reaching diesel levels of fuel efficiency with the hybrid powertrain”.
The outgoing CLA is officially capable of around 55mpg when equipped with a 2.0-litre diesel engine – and Autocar’s testers found it easy to achieve 60mpg+ at a cruise – and if the new M252 gets close to that, it could be one of the most efficient petrol engines in its class.
The 27bhp EV motor is able to power the car for short distances on its own at speeds of up to 62mph, drawing its power from a 1.3kWh 48V battery – also packaged as tightly as possible – under the front passenger seat. Charging is via recuperation at up to 25kW under deceleration.
Using the electric motor to start the engine means Mercedes could do away with the need for a conventional starter motor, so the start-stop function is “almost imperceptible for the driver”.
