The BMW S58: The Engine in Our G80 M3s, Explained

The S58 replaced the S55 with the G80 generation and addressed almost every complaint enthusiasts had about the engine that came before it. Both our G80 M3 Competitions run it, and it is the reason the current car feels like a meaningfully different animal from the F80 rather than an updated version of it.

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Built to Fix What People Complained About

The S58 did not appear in isolation. It arrived after several years of the S55 being criticised - fairly or not - for cooling under sustained hard use, and for a bottom end that some tuners considered a limiting factor for serious power increases.

BMW's M division addressed both directly. The S58 uses a closed-deck block, which is structurally stronger than the S55's open-deck design and better suited to high cylinder pressures. It received a stronger forged crankshaft, revised turbochargers, and - notably - an additional radiator specifically to cope with sustained high-load driving, the kind a track day or a long, hard mountain run would produce.

None of that is marketing language. It is a direct engineering response to a specific set of criticisms, and it is why the S58 has quickly earned a reputation as the more robust of the two engines, even though it is also the more powerful one.

The Numbers

In Competition specification - both of our G80s - the S58 makes 375kW, which is 510 horsepower, and 650Nm. Against the F80 Competition's 450hp and 550Nm, that is a genuine step: 60 more horsepower and 100 more Newton-metres from the same 3.0-litre twin-turbo six-cylinder layout.

More significant than the peak figures is where that torque is available. The S58 holds close to its maximum torque across a wider band of the rev range than the S55 did, which is why the G80 feels strong at almost any point in a gear rather than needing you to find the right revs.

Why the G80 Feels Different From the F80

Drive both back to back and the S58 is the more obviously capable engine in every measurable way, and also the less dramatic one in a specific sense: it does its job with less apparent effort.

The F80's S55 feels like it is working, particularly the tuned version - there is turbo chatter, a sense of boost building, moments where the engine feels like it is being asked something. The S58 in the G80 delivers comparable or greater performance with a flatter, more effortless character. It is the difference between an engine that shows you its work and one that simply produces the result.

Which of those you prefer is genuinely a matter of taste, and it is a large part of why the F80 versus G80 comparison does not have a single right answer.

xDrive and the S58

The S58's substantial torque is also the reason xDrive matters as much as it does on the G80. 650Nm through two wheels, especially in the wet, is genuinely demanding of the driver. The same torque through four wheels via xDrive is dramatically easier to deploy fully.

This is covered in detail in the xDrive versus rear-wheel-drive comparison, but the short version is that the S58's extra torque, relative to the S55, is a meaningful part of why the all-wheel-drive option exists on this generation and not the last one.

The Cooling Story, in Practice

The additional radiator BMW fitted to the S58 is not a spec-sheet curiosity. It reflects a genuine engineering priority: keeping the engine within its operating window during sustained hard driving, which is exactly the scenario a hired M3 on a good road for a full day represents.

Practically, this means the S58 is more tolerant of a spirited drive that goes on for hours rather than minutes. It is not a claim that the S55 overheats in normal use - it does not, in ordinary road driving - but the margin is wider on the newer engine, which matters more the harder and longer you drive.

What This Means for Your Booking

If your priority is outright capability - more power, more torque, more margin for a long, hard drive - the S58 in either G80 is the stronger engine, and it comes with the option of xDrive to put that capability down.

If your priority is the more analogue, more involving character that comes from an engine that feels like it is working, the S55 in either F80 - particularly the tuned one - is the one that delivers it.

Both engines are excellent at what they were built to do. They were simply built to do slightly different things, four years apart, by the same engineering team responding to feedback on the car before.

Everything about choosing between the cars that carry them is on the M3 hub.

The Closed-Deck Block, Explained Simply

This is the single most-cited engineering difference between the S55 and S58, and it is worth explaining rather than just naming.

An engine block is "open-deck" when the cylinder walls are only supported at the top, with open water jackets around them for cooling. It is lighter and cheaper to produce, and it is what the S55 uses. It is also, under very high cylinder pressure - the kind extreme tuning produces - a structural limitation, because the cylinder walls have less support against distortion.

A "closed-deck" block, which the S58 uses, adds material connecting the cylinder walls to the outer block structure at the top, closing off that open water jacket. It is heavier and more expensive to produce, and it is substantially stronger under high cylinder pressure as a result.

For a factory-specification car - both of our G80s are exactly that - this makes no difference you will ever feel. Where it matters is at the extreme end of aftermarket tuning, where S58 builds have shown they can support significantly more power than an S55 block before requiring the kind of internal work that turns a tune into a rebuild. It is a forward-looking piece of engineering rather than something that changes how the car drives today.

Why BMW Added a Second Radiator

The S58's additional radiator - beyond the standard engine cooling circuit - is dedicated to keeping intake air temperature down after the turbochargers compress it.

Compressing air heats it, and hot air is less dense, which means less oxygen per cylinder fill and less power. Every turbocharged engine manages this with an intercooler; the S58's arrangement is simply more capable than the S55's, reflecting the additional heat load of a more powerful engine used harder for longer.

The practical benefit shows up specifically under sustained load - a long uphill run at pace, repeated hard acceleration, the kind of driving a full day on a good road with a G80 actually produces. The S58 holds its power more consistently across that kind of use than the S55 does, which is a genuine, measurable difference rather than a marketing claim.

The S58 Beyond the M3

Worth knowing because it affects how mature and well-understood the engine already is, despite being newer than the S55.

The S58 first appeared not in the M3 but in the X3 M and X4 M, BMW's performance SUVs, which launched slightly before the G80 M3 itself. That means the engine had already accumulated real-world running in a heavier, harder-worked application before it reached the car most associate it with.

It has since spread across BMW's M range - the M4, the X5 M and X6 M in various states of tune, and other applications sharing the same fundamental architecture at different power levels. The Competition specification in our G80s, at 510 horsepower, sits toward the higher end of what BMW has released the engine in, without being the absolute maximum the company has extracted from it in limited-run CS and CSL models.

That breadth of application is a genuine reliability signal. An engine BMW trusts across sedans, coupes and heavy SUVs, at outputs from the low 500s to considerably higher in specialist models, is an engine the company has a great deal of confidence in - more so than a design used in a single, narrow application would suggest.

For a hirer, the practical takeaway is simple: this is not a new or unproven design wearing a big number. It arrived already tested hard, in heavier cars, before it ever sat in the M3 you would be driving.

It is also, quietly, one of the reasons we felt comfortable adding an all-wheel-drive M3 to the fleet at all - an engine already proven under the extra load and weight of an SUV application is a known quantity in a lighter, quicker saloon.

Read that alongside xDrive versus rear-wheel drive if you are deciding which G80 to book, since the engine and the drivetrain question are really one decision wearing two headings.