2024 Mercedes-AMG SL 43: Cart outclassing the horse

Last year marked a new generation for the Mercedes SL, including some significant changes to this stalwart of Stuttgart luxury. All-wheel drive is a first, standard on SL 55 and SL 63. Then there’s that second row of seats—this is the first SL in the U.S. to seat four since the R107 generation’s SLC, back in the 1970s. (The subsequent R129 did offer rear seats in Europe.) More important, perhaps, is that the SL is now a fully AMG-developed model, effectively a topless version of the AMG GT coupe. Nevertheless, Mercedes has seen fit to offer a more tame version of the SL roadster, sans fire-breathing twin-turbo V-8. Behold the 2024 Mercedes-AMG SL 43, which we drove for a few late-summer days earlier this month.

Because Mercedes model names and designations practically require a decoder ring these days, allow us to assist: The SL 43 is the entry-level, turbocharged four-cylinder model, equipped exclusively with rear-wheel drive. That information suggests that lightness is a priority in the SL 43, and the model’s press release does reference weight reduction—an astonishing 16 times. Weight reduction is also one of the reasons AMG selected the M139 four-cylinder, an AMG spokesperson told Hagerty. (Another reason: the inline-four offered better packaging, and thus, superior weight distribution, than Mercedes’ inline-six.) The M139 is complemented, in the SL 43, by legitimate lightening measures—a soft rather than a hard top, aluminum composite construction, forged aluminum suspension and steering components, and composite-metal brakes, to name a few.

Still, the SL 43 comes in at 3825 pounds, exceeding the Porsche 911 Carrera Cabriolet by—get this—288 pounds. We’re talking a silverback gorilla of mass difference here, despite that the 911 has two extra cylinders. Why so strapping? Footprint, for one: The SL 43 is 7.3 inches longer, 2.5 inches wider, and 2.4 inches taller than a 911 Cab, with a whopping 9.8 inches more wheelbase. It also boasts wonderful luxuries such as massaging front seats with heaters built into the headrests (Airscarf, in Mercedes speak), so you can parade across the interstate in your own little private spa.

Specs: 2024 Mercedes-AMG SL 43

Price: $111,050 (base); $117,035 (as-tested)
Powertrain: 2.0-liter turbocharged I-4 with electric belt-driven starter-generator; nine-speed multi-clutch automatic transmission
Horsepower: 375 @ 6750 rpm
Torque: 354 lb-ft @ 3250–5000 rpm
Layout: Rear-drive, two-door, four-passenger convertible
Weight: 3825 pounds
EPA-rated fuel economy: 21/27/23 mpg city/hwy/combined
0–60 mph: 4.8 seconds
Top speed: 170 mph
Competitors: Porsche 911 Cabriolet, Lexus LC 500 Convertible

Apart from all this, the SL 43’s M139 four-cylinder engine is paired with a 48-volt mild-hybrid system, a technology not known for its light weight. Mercedes does not specify the size or weight of the onboard battery, but we know that the electric motor is teeny tiny, only 1.6 inches wide. The idea here is faster throttle responsiveness and better low-end torque; the motor is meant to spin up the turbo right away until exhaust gasses can take over in conventional fashion.

Whereas past versions of Mercedes-AMG hybrids—such as the six-cylinder AMG GT 53 4-Door and AMG E 53—used a small electric supercharger to perform a similar function, the 48-volt system in the SL 43 powers both a belt-driven starter generator and that little electric motor. The e-motor is integrated directly into the turbo housing so that it can spin the turbocharger shaft in the most efficient manner. Mercedes is very proud that this tech trickles down from the AMG Petronas Formula 1 team. The starter-generator can provide 14 hp of additional grunt in certain situations, on top of the 375 made by the engine.

None of this performance comes without an AMG-worthy price—$117,000 as tested. Our loaner car’s options list included aluminum exterior trim ($750), 21-inch AMG Y-spoke wheels ($2450), a suite of driver assistance features ($1950), plus a few other odds and ends. That seems like a lot of spaetzle until you price out a 911 Cabriolet with comparable equipment, much of which comes standard on the Mercedes but costs extra on the Porsche: sport exhaust, keyless entry, a high-end Burmester surround-sound audio system, seats that are heated and ventilated. You quickly end up with a 911 that costs north of $140,000. Yikes.

As a luxury environment, the SL 43 far outshines a base 911. It’s more beautiful, for one, wearing a truly elegant design that seems to have been envisioned as a roadster from the start. (Every 911 Cabriolet looks like, well, a 911 coupe with its roof slashed off.) The SL’s leather is rich and soft. At night, the ambient lighting provides a futuristic, spaceship-like atmosphere. (Maybe too spaceship-like for some, who may also balk at the giant tablet screen and haptic-touch steering wheel functions.) Seats are all-day comfortable. Even the round little air vents possess a pleasant weight when their position is adjusted, something we are certain a cadre of German engineers fussed over for weeks.

This hybrid four-cylinder, on the other hand, does not feel ready for prime time. It’s a coarse, clinical torque-implementation device compared with AMG’s characterful twin-turbo V-8, or even with Mercedes’ silky straight-six. When fired up, the engine sounds on the rough side of raspy, a note accompanied by unpleasant idle vibrations and resonances in the cabin. In the CLA45, the hot hatch that debuted this M139 engine in 2019, some of these characteristics seemed to complement the car’s youthful, pocket-rocket attitude. Farty four-pot upshift noises seem all wrong in this otherwise-distinguished SL.

The engine is paired with a nine-speed automatic transmission, a multi-clutch affair that uses a wet start-off clutch in place of a traditional torque converter. It’s smooth off the line, but the gearbox programming is frustratingly hesitant to downshift in city conditions. You notice this most when attempting quick maneuvers, like a quick lane-change followed by sharp acceleration to match traffic speed. When the downshift arrives, a second and a half or so later, your opening has often passed—or you’ve completed the lane change and cut somebody off in your $117,000 car. The automatic top might fold in 15 seconds, but trust us, that’s not quick enough to protect you from a targeted barrage of expletives in Metro Detroit.

Once you start caning it on a back road, the SL 43 finds an easier rhythm. The powertrain is much happier in its mid- and upper range than at its low end, and the gearbox programming reacts more like you’d expect when speed and steering input increase. Throttle response is excellent in these conditions, and the four-cylinder makes plenty of power way up to redline, with peak power at 6750 rpm. On the way there, however, thrills are few. Torque delivery is more of a steady stream than a dramatic swell, and the whole experience falls shy of the muscle-car emotion that once defined AMG engines. If you treat the SL 43 as a long-distance cruiser, however, the four-cylinder is happy to play that part. It’s smooth, reasonably quiet, and comfortable at 80 mph, with usable torque even in eighth and ninth gear.

It’s really a shame about the engine, because this might be the most well-rounded chassis of any modern AMG product. For a car so long and wide, the SL is wonderfully balanced and agile. The rear end naturally follows the front, such that you rarely need to make steering adjustments to reposition the car on twisty roads. Using conventional dampers, the suspension walks the line between controlled and supple. Fine body motions communicate what the chassis is doing without making it feel unsettled. More often than not we looked down at the speedometer and saw a number 15 or 20 mph higher than we expected. Whereas the outgoing AMG GT roadster was overly stiff on bad pavement, the SL subtly squats over rough bits and keeps on going, not a care in the world. Brakes are responsive, with strong pedal feel and consistent behavior throughout the stroke.

This is fundamentally a luxury roadster, but it can roll up its cuffs and satisfy when need be. If it’s raw speed you’re after, the 911 is appreciably faster, more rewarding to drive quickly, and much more alert-feeling in city traffic. For something more stripped down there’s always the Lotus Emira, which in base form uses this same AMG engine.

We have a few other quibbles. The SL 43’s convertible top cannot be operated immediately when the car starts, which is usually the first thing you want to do before backing out of the driveway, and the system takes a few seconds before it’ll accept the command—either a swipe on the tablet or a double-tap of a physical button beneath the screen. Second, morning condensation on the windshield tends to bead up into larger drops and drop over the A-pillars, often onto the driver or passenger’s door-adjacent thigh. Last, the door handles never quite seem to work the way you expect them to; getting them to pop out from the doors requires reaching just so—not too fast! Pulling them to open the door seems to require the same monkish patience. Every passenger we took for a ride experienced the same phenomenon, which then required the driver to explain how the doors work with some insufferable phrase such as, “No, you have to open it like this.”

With some tweaking to this engine, or perhaps a different one entirely, the SL 43 would be quite a compelling alternative to the open-top Porsche 911, a Mercedes more concerned with comfort and grace than with corner-carving. With a base price of $111,050, it is more accessible than the next rung up on the SL ladder, the $137,400 SL 55, to say nothing of the $184,150 SL 63. Yet at the same time, no luxury roadster on the market so effectively combines refined chassis dynamics with the SL 43’s level of luxury and creature comforts. We suspect the powertrain will nonetheless be a deal-breaker on many test drives; even in 671-hp tune, it has won few friends in the new C 63 S E-Performance. Maybe AMG needs to take the hint and consider this miniature horse might not be fit to pull certain carts. Especially one as lovely as this SL.

2024 Mercedes-AMG SL 43

Price: $111,050 (base); $117,035 (as-tested)

Highs: Spectacular design. Uncompromising materials and luxury features. Refined chassis with handling that belies the car’s size.

Lows: Gruff engine. Lethargic transmission in city driving. Steering wheel busier than Shibuya Crossing.

Takeaway: A convincing modern-day Mercedes roadster in search of a deserving heart.

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