New Mercedes CLA gets 1.5-litre petrol with diesel-level efficiency

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 tuned 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 more than 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 electric 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".

Electric CLA bids for efficiency crown

The quest for efficiency has underpinned every facet of development for the MMA platform and its electric drivetrains, which have been engineered with heavy influence from the EQXX concept that recently travelled 628 miles across the Arabian desert at a whopping 8.4 miles per kWh.

Shortly after, the CLA proved its efficiency credentials by breaking the record for the longest distance covered in 24 hours by an EV, with a prototype driving 2410 miles around Italy's Nardò ring. 

Mercedes says the new drivetrain has potential to achieve 5.18mpkWh in real-world use – a hugely competitive figure for its segment – and returns a battery-to-wheel efficiency figure of 93%. It is, the firm says, the "one-litre car of the efficiency age".

The MMA architecture underneath the CLA is equipped with 800V hardware as standard, for charging at up to 320kW, giving 10-80% top-ups in as little as 10 minutes – as proven during the Nardò run.

The CLA – and the EQA and EQB replacements that will follow – will be offered with a choice of 58kWh or 85kWh (both usable capacity) batteries, the latter with silicon-oxide anodes, which are said to boost gravimetric energy density by 20% compared with the cells current in use.