The W222 is widely considered one of the finest S-Class generations, rivalling the legendary W140 for long-term desirability. The S500 pairs the M278 4.7-litre biturbo V8 with the 7G-Tronic Plus automatic, delivering 455 PS of effortless performance; Mercedes' April 2016 price list already specifies the 9G-Tronic for the S 500, so later pre-facelift cars have the nine-speed. Cabin refinement and insulation are exceptional, and the car depreciates heavily, making it accessible on the used market. Complexity is the trade-off: AIRMATIC or Magic Body Control suspension, over 100 electric motors inside, and a dense engine bay mean that when things fail, bills are significant.· more· less
Exceptional refinement and comfortRobust M278 V8 bottom end
Air suspension repairs are expensiveCamshaft solenoid oil wicking risk
Buy if: You want flagship luxury at a fraction of the new price and can budget for specialist maintenance at a Mercedes V8 workshop.
Avoid if: You cannot absorb surprise repair bills above €3,000 or want low-maintenance ownership without specialist diagnostics.
Camshaft adjuster solenoid oil wicking into ECU harness
up to €8,0001 of 8
Oil seeps through solenoid seals and migrates along the wiring harness toward the ECU · more· less
The M278 has a well-documented design flaw where engine oil wicks through the camshaft adjuster solenoid seals and migrates via capillary action along the wiring harness. If caught early, replacing the solenoid seals and installing sacrificial pigtail harness extensions (approximately €15 each) costs €500-800 total at a specialist. However, if the oil reaches the ECU, the full repair including engine wiring harness and ECU replacement can reach €5,000-8,000. Mercedes released a protection repair kit to address this. Proactive owners install sacrificial pigtail harnesses preventively. Symptoms of advanced contamination include multiple simultaneous fault codes for oxygen sensors and ignition coils. This affects all M278 engines from 2011-2017 and is the single most important item to check before purchase.
AIRMATIC air suspension strut leak
up to €4,0002 of 8
Rubber air spring bladders perish and crack, causing one corner to sag overnight · more· less
The AIRMATIC suspension is standard on the W222 S-Class and the rubber bladders degrade with age and temperature cycling. Rear springs fail most frequently. Symptoms include one corner sitting lower after overnight parking or the compressor running constantly. OEM strut replacement at a dealer runs €800-1,200 per corner including labor. Aftermarket alternatives from Arnott or Bilstein cost €400-600 per strut. If the compressor pump fails from overwork due to leaking springs, add €500-900 for the pump. A full suspension refresh (4 struts plus compressor) can reach €3,500-4,000 at a dealer. Failures typically begin between 80,000-120,000 km. Cars equipped with Magic Body Control have even more complex and expensive suspension with hydraulic ABC pump failures potentially costing €2,000-5,000.
Timing chain tensioner wear (cold start rattle)
up to €5,5003 of 8
Check valve weakens in tensioners, causing metallic rattle on cold start for up to 30 seconds · more· less
Early M278 engines (2013-2014 production) are more susceptible to timing chain tensioner issues. The check valve weakens over time, allowing hydraulic pressure to bleed off overnight. This produces a distinctive rattle on cold start lasting 1-30 seconds. The M278 uses three chains (one primary, two secondary) with three tensioners. Replacing tensioners alone costs €2,000-3,000 at a specialist. However, replacing chains, guides, and sprockets simultaneously is strongly recommended, bringing total cost to €4,000-5,500. The rattle typically develops between 80,000-120,000 km. Mercedes improved the tensioner design from mid-2015 onwards. Ignoring the rattle risks chain skip and catastrophic valve-piston contact.
Valve cover gasket and oil leak
up to €2,0004 of 8
Plastic valve covers warp from heat, causing oil to drip onto the twin turbochargers · more· less
The M278 uses plastic valve covers that gradually warp from the heat generated by the turbochargers mounted in the valley of the engine. Once the cover distorts, the gasket cannot seal and oil drips onto the turbos, producing a burning oil smell. Simply replacing the gasket is not sufficient as the warped cover must be replaced as well. The repair involves significant disassembly including high-pressure fuel pump, injectors, and coils. Independent specialists typically charge €800-1,200, while Mercedes dealers quote €1,500-2,000 for both sides. This is among the most common M278 issues and affects most engines eventually, typically becoming noticeable between 80,000-120,000 km.
Turbo wastegate rattle and bushing wear
up to €5,0005 of 8
Wastegate bushings wear, causing rattling at partial throttle between 2,000-3,000 RPM · more· less
The twin turbochargers use internal wastegates with bushings that wear over time. The valve disk vibrates in its seat during partial load operation, causing a rhythmic rattle. Mercedes issued a TSB acknowledging this as a characteristic of the design and offers a software recalibration via Xentry (adding AO code 31O) that keeps the wastegate closed longer in partial load. If the rattling becomes severe or causes boost control issues, full turbo replacement is required. The turbochargers are welded to the exhaust manifolds and cannot be replaced without removing the engine, making labor costs substantial. Aftermarket wastegate repair kits with stainless steel bushings are available for €200-400, but turbo replacement per side runs €2,000-3,000 for parts plus €2,000+ for engine removal labor.
Parasitic battery drain
up to €8006 of 8
Control modules fail to enter sleep mode, draining the battery within 5-10 days of inactivity · more· less
The W222 has extensive electronics with over 100 electric motors and numerous control modules. When any module fails to enter sleep mode properly, parasitic draw exceeds the normal 40-80 mA range and drains the battery. The COMAND infotainment system, keyless entry receiver, and various driver assistance modules are common culprits. A new OEM battery costs €200-350, and diagnosing the parasitic draw (pulling fuses systematically with an ammeter) can take several hours at a specialist. If a faulty control module is identified, replacement runs €300-800. A quality trickle charger (CTEK MXS 5.0 recommended) is essential if the car sits for more than a week.
7G-Tronic and 9G-Tronic rough shifting
up to €2,5007 of 8
Rough upshifts and downshifts, especially 2nd-to-3rd gear, often resolved with software update · more· less
Many 2014-2017 W222 owners report rough or jerky shifting. Pre-facelift cars have either transmission, the 7G-Tronic early on and the 9G-Tronic by 2016, and on both the usual cause is degraded transmission fluid or a conductor plate losing calibration. Mercedes issued software updates that recalibrate shift points. A transmission adaptation reset combined with fresh fluid and filter costs €400-600 at a specialist. If the conductor plate (valve body electronics) has degraded beyond software correction, replacement costs €1,200-2,500. Mercedes technical material specifies recurring oil changes at 125,000 km for the NAG2FE+ fluid used in M278 applications; independent specialists recommend a more conservative 60,000 km.
Engine mount deterioration
up to €1,5008 of 8
Hydraulic engine mounts collapse, causing vibration at idle and low RPM · more· less
The M278 engine mounts are hydraulic and wear out over time, typically after 80,000-120,000 km. Failed mounts cause noticeable vibration through the cabin at idle and at low engine speeds (1,000-2,000 RPM), which is particularly jarring in a car designed for supreme comfort. Replacement requires careful work around the turbochargers and dense engine bay. OEM mounts cost approximately €200-350 each, and the job requires 6-8 hours of labor. Total cost including both sides runs €800-1,200 at an independent specialist and €1,200-1,500 at a Mercedes dealer.
Rewarding ownership if maintained, but complex and expensive when things fail
The M278 biturbo V8 has a proven bottom end that can exceed 200,000 km, and many W222 owners report years of trouble-free driving. However, the engine's known weak points (camshaft solenoid oil wicking, timing chain tensioners on early cars, valve cover leaks) require proactive monitoring. The AIRMATIC suspension is an expected wear item and the dense electronics generate parasitic drain and occasional sensor faults. A comprehensive pre-purchase inspection at a Mercedes specialist is essential, and owners should budget for annual maintenance costs that reflect the car's original price bracket, not its depreciated value.
Service history
Complete Mercedes dealer or specialist records essential. Verify oil changes every 10,000-15,000 km with approved 5W-40 or 0W-40 synthetic oil.
Tires
Check tread depth, date codes, and uneven wear patterns. Rear tires wear faster on this rear-wheel drive car. Expect 245/45R19 or 275/35R20 sizes.
Cold start
Must start the engine completely cold. Listen carefully for any rattling or ticking in the first 30 seconds.
Test drive
Minimum 30 minutes including highway speeds. Monitor gear changes, ride height consistency, and any warning lights.
Specific for this vehicle
Listen for timing chain rattle on cold start
Start the engine stone cold and listen for metallic rattle lasting 1-30 seconds. Any rattle indicates tensioner wear and is the most critical check on the M278.
Inspect AIRMATIC ride height and operation
Park on level ground and verify all four corners sit at the same height. After overnight standing, check that no corner has dropped. Listen for the compressor running constantly.
Check for burning oil smell from engine bay
Open the hood after a 20-minute drive. A burning oil smell from the centre of the engine bay indicates valve cover gasket leaks dripping onto the turbochargers.
+ 4 more checksShow less
Scan for multiple simultaneous fault codes
Use a Mercedes-compatible diagnostic tool to scan for codes. Multiple seemingly unrelated faults (O2 sensors, ignition coils) simultaneously suggest camshaft solenoid oil wicking into the harness.
Test transmission through all gears under load
Drive for 20+ minutes in varied conditions. Feel for harsh shifts, especially between 2nd and 3rd gear. Check if transmission adaptation resets fix rough shifting.
Listen for turbo wastegate rattle at partial throttle
At 2,000-3,000 RPM under light load, listen for a rhythmic rattling sound from the engine bay. This indicates worn wastegate bushings.
Verify panoramic sunroof recall completion
W222 models had a recall for the front sunroof panel potentially detaching. Confirm with Mercedes using the VIN that this recall has been completed.
Recalls and Technical Service Bulletins
Panoramic sunroof front panel detachment - UK recall R/2021/274, limited to cars whose panel may have been incorrectly bonded during an earlier service repairCritical - verify applicability and completion
Seat belt pre-tensioner propellant mixing ratio (June 2016 - March 2017 production)Verify completed
eCall communication module software failure (2016-2017 models)Verify completed
Electric power steering control unit soldering defect (S-Class production August 2012 - October 2015, which includes 2013 W222s)Verify completed
Steering gear bolt recall, KBA campaign 4694204 (W222 production through October 2017; applicability is decided by VIN)Critical - verify applicability and completion
Contact a Mercedes-Benz dealer with the VIN to verify all recalls have been completed. The steering gear bolt campaign 4694204 and the panoramic roof action are the safety-critical ones, and both are decided by VIN rather than by model year. A W222 Takata campaign is often quoted, but Mercedes France's affected-model list does not include type 222, so ask the dealer for the campaign code that applies to the car.
Warranty Status
Factory warranty (2 years)Expired on all W222 S500 models
Rust perforation warranty (30 years)May still apply on 2013+ models
Extended warranty availabilityAvailable through Mercedes dealers or third-party providers
All W222 S500 models are well outside their original 2-year factory warranty. Mercedes-Benz offers extended warranty packages through authorized dealers, but premiums are high for V8 models and coverage typically excludes AIRMATIC suspension and wear items. Independent warranty providers may offer more affordable coverage but read exclusion clauses carefully.
Sources: Research draws on model-specific owner forums and owner communities, recall information from official authorities, German automotive press, and multiple workshop cost references cross-checked against each other.
This report is for informational purposes only and does not constitute professional advice. Estimates may be inaccurate. Always have a qualified specialist inspect the vehicle before purchase. We accept no liability for decisions made based on this information.
