How to Replace Spark Plugs on BMW S58 - G80 M3, M4 DIY

The S58 is BMW's current twin-turbocharged M inline-six, powering the G80 M3 and G82 M4, and it is the most powerful production inline-six BMW has ever put in a road car. At 503 horsepower in Competition trim and 530 in CS spec, the S58 pushes the ignition system harder than any BMW engine before it in a street car. I have done spark plug jobs on early G80 M3s that came to my shop, and the experience is notably cleaner than working on the F80-generation S55. BMW improved access significantly with the G-chassis layout.

Last week I had a G82 M4 Competition come in for its first plug change at 30,000 miles. The owner had it Stage 1 tuned through MHD and was doing occasional track days at a local circuit. Smart guy - he did not wait for a misfire warning. When we pulled the plugs, the electrode wear was measurable but still within acceptable limits at 30,000 miles. At 60,000 miles on that tune and those track conditions, I am confident the plugs would have been marginal. BMW's 60,000-mile interval on the S58 is not wrong for a stock car driven conservatively, but it has no application to the way most G80 M3 owners actually use their cars.

I want to be clear upfront: the S58 and B58 use the same NGK plug part number at stock heat range. This is intentional - the B58 and S58 share architecture, though the S58 is substantially reinforced and modified. The stock plug is the same, but the intervals and colder plug recommendation diverge because of how differently the S58 operates versus the B58 in a 340i. More boost, higher revs, more heat. Same starting point, different maintenance needs.

S58 Spark Plug Part Numbers and Selection

The S58 stock replacement plug is the NGK ILZKAR7H11 - the same plug used in the B58. This is an iridium fine-wire plug at heat range 7. For a completely stock S58 on 91-93 octane pump gas with no map modifications and primarily street use, this plug at a 40,000-mile interval is defensible. But I do not see a lot of completely stock S58 cars. The G80 M3 and G82 M4 are tuned almost universally within the first year of ownership.

For tuned S58 applications - any map that increases boost above the Competition spec - step to the NGK ILZKAR8H11, one heat range colder. For track use on any tune, the ILZKAR8H11 is the right choice regardless. For extreme builds running port injection, E85, or high-boost Stage 3 setups, consult with your tuner on whether a second step colder is appropriate. In my experience, the ILZKAR8H11 covers most bolt-on and Stage 2 S58 builds adequately.

Torque spec: 25 Nm. No anti-seize on the plug threads. The NGK iridium plugs come with a nickel coating on the threads that handles the aluminum cylinder head interface appropriately. Dielectric grease on the inside of the coil boot where it contacts the plug ceramic insulator - thin coating, wipe off any excess.

G80 M3 vs G82 M4 Access Comparison

One of the genuine improvements in the G-chassis M cars over the F-chassis is engine bay access. The G80 M3 sedan has excellent top-of-engine clearance - the S58 sits in a relatively spacious engine bay compared to the tightly packed F80. All six coil packs are accessible from directly above with the engine cover removed. I can work on any of the six cylinders without moving any ancillary components.

The G82 M4 coupe is slightly more constrained because of the lower hood line, but the difference is marginal in practice. I have done plug changes on both body styles and found them essentially identical in difficulty. The G83 M4 convertible is the same engine bay as the coupe. In all three cases, the procedure is engine cover removal, coil removal, plug removal, plug installation, coil reinstallation - clean and direct.

The engine cover on the G80/G82 M cars is carbon fiber or a carbon-look plastic depending on the specification. Remove it carefully by lifting straight up after releasing the retention clips at the front. Set it on a soft surface - cracking the carbon fiber cover by dropping it or leaning something against it is an expensive mistake. The covers are several hundred dollars to replace.

Step-by-Step S58 Spark Plug Replacement

Cold engine - overnight minimum. The S58's high-compression twin-turbo design retains heat in the cylinder head for a long time after driving. I have put a thermal camera on S58 cylinder heads and found plug well temperatures still above 60 degrees Celsius three hours after the engine was shut off. Let it sit overnight and start the job cold.

Remove the engine cover. On Competition spec cars with the carbon fiber cover, there are typically four retention points. Lift straight up with even pressure and set it somewhere safe. You are now looking at the top of the S58 - a clean inline-six layout with six coil packs running along the valve cover, the twin turbocharger wastegate actuators visible at the rear, and the charge pipes running along the sides of the engine.

Working from cylinder 1 at the front of the engine, disconnect the coil connector - press the tab and pull back. Grasp the coil body and pull firmly upward. The S58 coil boots are well-fitted and will require steady upward force to release from the plug. Do not pry. If a coil is stuck, apply steady upward pressure while simultaneously giving it a slight twisting motion - this breaks the vacuum seal in the boot and allows it to release.

Insert the 14mm thin-wall spark plug socket on a 6-inch extension, seat it on the plug hex, and break it loose counterclockwise. On a first-time plug change on a G80, the plugs are unlikely to be overtightened from the factory and should break loose without excessive effort. If they do not, check that your socket is fully seated on the plug hex before applying force - a partially seated socket can slip and round the plug hex, which complicates removal significantly.

Spin the plug out by hand after breaking it loose. Inspect it - on a 30,000-mile tuned S58, you should see some electrode wear and moderate deposits on the firing tip. Measure the gap if you want confirmation of the wear. Thread the new plug in by hand, all the way in by hand before applying any tool. Torque to 25 Nm. Apply dielectric grease inside the coil boot and reinstall the coil. Repeat for all six cylinders.

S58 vs S55 - Differences That Matter for Plug Maintenance

Having worked on both generations of M inline-six, the S58 is a meaningfully cleaner design for maintenance purposes. The S55's twin-turbo plumbing ran in a way that created more obstacles around the top of the engine. The S58's layout is more logical, with the charge routing doing less to obstruct the coil and plug access.

The S58 also runs lower boost pressure in stock trim than many tuned S55 builds, though its higher displacement and improved efficiency mean it makes more power at that boost level. For plug maintenance purposes, this means the stock S58 is not necessarily harder on plugs per mile than the stock S55, even though it makes more power. The tuned S58 is a different story - tuners are getting remarkable power numbers out of these engines with relatively modest boost increases, and those tunes do require the colder plug and shorter intervals.

One thing I track closely on S58 engines: detonation. The S58's control systems are very sophisticated and the DME will pull timing aggressively if it detects knock events. But a plug that is borderline worn can cause combustion instability that the knock sensors may or may not catch before it causes harm. Fresh plugs remove this variable entirely. On a car worth as much as a G80 M3, the cost of plugs every 25-30K is irrelevant insurance.

Coil Packs on the S58

The S58's coil packs are an improvement over the S55 units. Fewer coil failures at moderate mileage, better electrical performance under high-demand conditions. On stock or mildly tuned S58 builds, I am not seeing the coil failures that were common on tuned S55 cars. That said, on heavily tuned builds or extreme track builds, coil upgrades are available and make sense.

For a standard plug change on a stock or Stage 1 S58, inspect the coil boots as you remove them. Look for cracks in the rubber, ozone damage, or oil contamination. If everything looks clean, reuse the coils with fresh dielectric grease. On a car above 60,000 miles or with heavy track use, proactive coil replacement alongside the plugs is smart. The labor is already done. For more on the G-chassis M cars, see our G20 model page, the spark plug and ignition section, and the B58 engine guide for context on the S58's relationship to the production engine family.

S58 Port Injection System and Plug Maintenance

The S58 features a combined direct and port injection system - unlike the B58 which is direct injection only, the S58 uses port injection nozzles in addition to the direct injectors. This combined injection approach solves the carbon buildup problem inherent in direct-injection-only engines. The port injectors provide a fuel wash on the intake valves during certain operating conditions, keeping the valves cleaner over time. This is good news for owners because it removes walnut blasting from the maintenance schedule that S55 and N55 owners had to deal with.

From a spark plug maintenance perspective, the combined injection system means the combustion events are very precisely controlled. The DME manages the split between direct and port injection based on load, RPM, and temperature. Under high load - which is when you are most concerned about spark plug condition - the injection ratio shifts toward direct injection for maximum charge density. This is exactly when you need your plugs to be in optimal condition. A worn plug under peak S58 load conditions is a liability; the engine's sophisticated combustion management cannot compensate indefinitely for a firing event that is misfiring or timing inconsistently.

G80 M3 xDrive vs RWD - Plug Access Differences

BMW introduced all-wheel-drive (xDrive) as an option on the G80 M3, which was a first for the M3 nameplate. From a plug change perspective, the xDrive M3's engine is identical to the RWD car - the S58 is the same unit in both configurations, and the engine bay access is unchanged. The xDrive hardware is all below the engine, in the driveline rather than affecting engine bay layout. I have done plug changes on both RWD and xDrive G80 M3s and there is zero practical difference in the procedure.

The G82 M4 is offered only in RWD in Competition spec (with a manual option returning), and the M4 Competition xDrive. Same situation as the M3 - the engine bay is identical and plug access is unchanged. If you are an xDrive M3 or M4 owner reading this wondering if your car has some special consideration for plug maintenance, the answer is no. Do it the same way described here. For more on the current-generation M3 and M4 platforms, see our G20 platform guide and the B58 engine article for context on the S58's relationship to the B58 family.