2024 Mercedes-Benz S-Class Diesel: Still Excellent, If Anybody Cares

Diesel passenger cars were barely more than a statistical blip in the United States, but they conquered the European market. The peak came in 2011, when no fewer than 56 percent of the cars sold across the European Union had compression-ignition engines. In some countries the proportion rose much higher; pity anybody selling spark plugs in France in 2008, when a full 77 percent of new cars ran on diesel.

Things have changed dramatically since then. Last year just under 14 percent of the cars sold in Europe were diesel—a smaller percentage than EVs—and yet it remains a popular choice in some parts of the market. These include luxury sedans and the reason that brings us here—the Mercedes S450d L we recently got the chance to experience in some wintry conditions in Germany and Switzerland.

Despite this fall from fashion, there remains a huge amount to like about a good diesel engine—and very few are better than the turbocharged six-cylinder that Mercedes offers in the S-class for certain markets. This is a 3.0-liter turbodiesel that was introduced in 2017—just months after Volkswagen had agreed to pay $4.3 billion to settle its infamous emissions-cheating scandal in the U.S.—and since then it has been offered in most of the company’s larger models in Europe. The 2024 S-class offers two different specs of the same base engine, the S350d making a peak of 308 horsepower and the brawnier S450d we drove rated at 362 horsepower.

That number is impressive by itself, especially for anybody old enough to remember the 300SD and its 120-hp five-cylinder turbodiesel that was launched in the States in 1979. But the S450d’s maximum power output is also a largely irrelevant statistic, as owners are likely to only rarely push their cars to 4000 rpm, the point at which it’s delivered. But they will experience the peak torque—a mighty 553 pound-feet available between 1350 rpm and 2800 rpm—every time they drive the car.

This relaxed muscularity defines the way the long-wheelbase S450d L drives—and suits its luxurious purpose perfectly (shorter-wheelbase, non-L models with 4.3 fewer inches between their axles are available in some markets). The car’s low-speed manners are exemplary, with gas and brake allowing for almost imperceptible starts and stops. Once rolling, the software controlling the standard nine-speed automatic transmission upshifts early to keep revs low, yet the rate of acceleration barely seems to diminish as speed rises. This is a car that can accelerate from rest to a 100-mph cruise without the engine ever going past 2000 rpm or the driver needing to press the accelerator more than a quarter of the way to its stop. As a definition of effortless, that’s hard to beat.

There are no obvious compromises on refinement compared to the standard S500 model. No current-generation S-class is vocal under anything except hard use, and at idle the S450d is no louder than its gasoline sibling. On the move, the diesel engine produces a subdued hum, its cabin staying as hushed as that of any other current-generation S-class. Only when pushed hard does the S450d develop a distinct voice, a muscular thrum a little like that produced by a hard-working but well-insulated turbine. We weren’t able to confirm Mercedes’s claimed 155-mph top speed on the autobahn, but only because our test car’s winter tires were only rated to 149 mph. So we drove at 149 mph instead.

But the diesel S-class was almost equally impressive when asked to deal with heavy snow in the Swiss Alps. Conditions were bad enough to cause the cancellation of the St. Moritz ice concours we were meant to be attending—one held on a frozen lake that it was feared would struggle with the weight of the snowfall. But even in treacherous conditions on unplowed roads the S450d’s all-wheel drive and stability management found grip and traction—even as many of the generally well-prepared Swiss drivers were struggling to keep rolling.

Beyond badging, and the fact the digital tachometer’s redline is marked at a lowly 4000 rpm, the S450d is effectively identical to look at and touch as its gasoline-powered siblings. The beautifully finished cabin is supremely comfortable and a great place to spend serious time—we still felt fresh after multi-hour stints behind the wheel. But the diesel also shares the same frustrations as the rest of the range, including the overly complex UI system, the continued experience of which has not made us grow any fonder of it. But a definite highlight in tight-fitting European towns and cities is the rear-axle-steering system, which makes the S-class impressively wieldy for something so large.

In Germany, the S450d costs less than comparative S500 models; the S450d L opens at the equivalent of $128,500. Yet for most buyers the diesel’s most impressive virtue in its European homeland is its fuel economy. The official mileage number of the continent’s generous WLTP test cycle is the equivalent of 38 mpg. While we didn’t achieve that, we did see the onboard trip computer reporting 27 mpg after a 200-mile journey that had included long stretches of high-speed autobahn cruising. We know that diesel is dead and almost certainly buried when it comes to passenger cars in the U.S., and Europe won’t be much further behind. But the S450d is a reminder of just how good the best diesels are.

Source: Reviews - aranddriver.com