Forget The AMG: The Best Mercedes S-Class Has A Straight-Six

Mercedes is busy readying the next S-Class. And while Stuttgart’s fleet of SUVs is of more financial importance these days, a new version of the luxo-barge is still a huge deal.

The S-Class has long been a portal into the future - a look at the kind of tech that’ll eventually trickle down to much more humble cars. Adaptive cruise control, four-wheel Bosch ABS and even crumple zones - they all appeared first on an S.

The current, soon-to-be-retired version of the car - the W222 - is no different. Its headline tech features include Magic Body Control, which scans the road ahead and ‘prepares’ the adaptive suspension as necessary, and, erm, an on-board fragrance system.

With such a focus on tech, the engines almost play second fiddle. But since you have to choose one, which is the pick of the litter? Helpfully, the line-up of the new one will largely mirror the W222’s, so anyone stumbling on this page in a few months will find it semi-relevant still. Rumour has it, there will even - against all odds - still be a twin-turbo V12 available.

But unless you have more wealth than a small country, the 12-cylinder depreciation bomb is best avoided. I’m always partial to a Mercedes with an AMG V8 and applaud Affalterbach for creating the S63, but a snarling V8 does not make for the ideal S-Class. A diesel engine is fine in an E-Class but not quite befitting of an S, although given how many of them do galactic mileage, it’s understandably a popular and sensible choice. I’m not sure I’d go for the S560 V8; if you’re doing the eight-cylinder thing, surely it’s got to be the AMG?

There’s also an S560e, which - confusingly - is a plug-in hybrid V6. The best S, though, has an inline-six petrol engine. My first experience of this engine first came with the AMG CLS 53, but with the expectation associated with those three letters, it seemed to missed the mark. When trying it again in the S500 L, though, it all made sense.

This is the ideal engine for a wafty S-Class. It’s smooth, quiet and civilised, and thanks to the 48-volt mild-hybrid system, reasonably responsive when you need it to be. The ‘EQ Boost’ system uses an electronic compressor which provides an additional 21bhp and 184lb ft of torque (no, that second bit isn’t a typo) for just under a second.

It’s potent, too. Even before the EQ boost thing comes into play, the 3.0-litre turbo engine is good for 429bhp and 384lb ft, making for a 0-62mph time of 4.8 seconds. That’s just a couple of tenths off the 6.2-litre N/A V8-powered W221 S63. It gathers speed in a more discreet, unassuming manner, of course, but that’s the appeal; this is an attitude that’s more in tune with the S-Class remit.

It’s not a perfect engine, however. The official combined economy figure of 38mpg sounds impressive, but in the real world, hitting mid-30s on an extended cruise (we did a couple of very long stints in ‘our’ S500L test car) takes some effort. Also, what little noise you can hear from the inline-six isn’t of the most inspiring variety.

But as a blend of effortless performance and waft-friendly refinement, it’s brilliantly judged. And yes, I appreciate some will be triggered by the ‘S500’ name - long associated with a V8 - being used for a 3.0-litre I6, but move on. There’s a time and a place for eight-cylinder engines, but I reckon the S-Class is better when it doesn’t have one, and I’m not expecting that to change.