2026-04-08 14:47:22

Mercedes Plans to Replace the SL’s Four-Cylinder Engine with a More Powerful Inline-Six

Mercedes-Benz intends to swap out the SL’s current four-cylinder powerplant for a straight-six engine.
This modification is driven by the need to comply with stricter emissions standards.
The facelifted SL53 model is expected to debut in 2027 with these updates.

Mercedes-Benz is preparing a significant update for the base SL model. With the planned 2027 refresh, the automaker will retire the four-cylinder engine in favor of a six-cylinder inline unit.

According to a recent report from Auto Motor Und Sport, the M139 four-cylinder engine found in the SL43 will be discontinued due to its inability to meet the upcoming Euro 7 emissions requirements. Its replacement is likely to be the M256 Evo, a 3.0-liter inline-six mild-hybrid engine, rebranded as the AMG SL53.

This new powertrain is expected to deliver 449 horsepower, complemented by a 23-horsepower integrated starter-generator. Additionally, the SL53 will feature all-wheel drive as standard equipment, marking a change from the rear-wheel-drive setup of the SL43.

Upgrades to the V8 Models

The report also mentions revisions to the V8 engines powering the SL55 and SL63 variants. The 4.0-liter twin-turbo V8 will transition from a cross-plane crankshaft to a flat-plane crankshaft design, which enhances performance while adhering to the new emissions criteria.

Power figures are expected to rise to 537 horsepower for the SL55 and an impressive 650 horsepower for the SL63. Currently, the SL55 produces 469 horsepower and 516 lb-ft of torque, while the SL63’s output climbs from 577 to 650 horsepower.

While there are no specifics yet on the SL63 S E Performance plug-in hybrid model, which combines the V8 with an electric motor and currently makes 805 horsepower, it’s hoped that the updated V8 could push this figure beyond 880 horsepower.

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