The Inline-Six Engine Is Back For Mercedes-Benz

Illustration for article titled The Inline-Six Engine Is Back For Mercedes-Benz

The updated 2018 Mercedes S-Class is the first new Benz to get the company’s glorious new 3.0-liter straight-six engines. How happy am I? Very happy.

The first new I6 that the S is getting is the OM656 diesel, which comes in two different configurations. There’s a low-spec version that makes 286 horsepower and 442 lb-ft of torque. That’s in the S 350d.


(Again, this is a 3.0-liter engine. It’s really 2,925 cc to be exact. Mercedes gave up common-sense names a long time ago.)

There’s also a high-spec version that makes 340 horsepower and 516 lb-ft of torque. That’s in the S 400d, though the displacement is unchanged. (Again again, Mercedes names make sense.)

This is a bit more power than Mercedes itself projected when it first announced this engine late last year.

The OM656 diesel
The OM656 diesel

I wish I could be particularly clear about how this engine is turbocharged, but Mercedes does not ever actually mention a turbo in the engine’s dedicated press release from last year, and it’s kind of vague in its newest press release today. I believe it’s a twin-scroll single turbo, but here’s how Mercedes puts it:

The special traits of the top-of-the-line engine in the diesel family include the stepped-bowl combustion process, two-stage turbocharging and for the first time the use of CAMTRONIC variable valve-lift control. Its design features a combination of aluminium engine block and steel pistons as well as further improved NANOSLIDE® coating of the cylinder walls.


Mercedes talks a lot about how this new diesel meets new real-world emissions standards in Europe but makes no mention of selling in the Unites States.

Hm. I wonder why.

The M256 gas engine
The M256 gas engine

Coming up soon is the most desirable new I6: is the ‘M256' code gasoline engine. This one is not one of the debut engines for the new S Class but Mercedes says it’s coming soon. It’s the same 3.0 liter displacement, but it’s a gasoline engine with an electric turbo, which spins with the assistance of an electric motor. That should kill turbo lag, Mercedes argues.

This M256 makes a good 408 horsepower and 370 lb-ft of torque. Can I wait for America to get this engine? No. I am currently looking at flights to Stuttgart to go hijack some engines myself to go stuff them into a R107 SL from the ‘70s.


It’s going to be a rally car. It’s going to be awesome.

Raphael Orlove is features editor for Jalopnik.

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PotbellyJoe and 42 others

Put that 300d unit in here and we’ll talk MB.

Anyone poo-pooing this idea has no idea what the joy of interchangeable seating means for a guy with growing boys and a passion for bicycles.

(Also, a diesel Metris is much more enticing than the diesel Transit for me, I don’t want something quite that large/tall)