Mercedes-Benz S450 W222

The W222 uses AIRMATIC air suspension on all four corners as standard. The rubber air spring bladders develop internal cracks and leaks over time, causing the car to sag on one or more corners when parked overnight. The compressor then runs overtime to compensate, accelerating its own wear. A single strut replacement costs approximately €800-1,200 for an aftermarket unit (Arnott, Bilstein) or €1,200-1,800 at a Mercedes dealer. It is strongly recommended to replace struts in pairs (left and right), doubling the cost. The air compressor itself costs €800-1,200 to replace. If multiple components fail simultaneously, total bills reach €3,000-4,000. AIRMATIC components on the W222 typically last 80,000-130,000 km depending on road conditions and climate. Age matters as much as mileage: rubber degrades regardless of use.

The S450 uses a rear-mounted 48V lithium-ion battery to power the EQ Boost mild hybrid system (ISG, eBooster, electric water pump). Premature failure has been reported, sometimes under 80,000 km. Symptoms include warning lights for the EQ Boost system, erratic start-stop behavior, loss of power assist, and reduced fuel efficiency. Mercedes identified a manufacturing problem on some early units where paint on the housing interfered with proper grounding. Battery replacement costs approximately €2,000-3,000 at a dealer. Independent specialists with 48V expertise may offer repair or reconditioning for €1,500-2,000. A class action lawsuit regarding sudden battery failures across multiple Mercedes models suggests this is not an isolated problem.

The M256's ISG sits between the engine and the 9G-TRONIC transmission, functioning as both the starter motor and alternator while also providing electric torque assist. When it fails, symptoms include a no-start condition or, more dangerously, a sudden shutdown while driving. The primary warning sign is a '48V On-Board Electrical System Malfunction' message. Replacement requires removing the transmission to access the unit, which drives the high labor cost. Total repair costs range from €3,500-6,000 depending on whether a new or remanufactured unit is fitted. This failure is reported more frequently on 2020-2023 C300 and E350 models with the M264/M256 engines than on the W222 S450, where it remains a low-probability but high-cost concern.

The M256 shares a family trait with the M276 and M278: oil seepage from the upper timing cover gaskets. Mercedes issued TSB LI01.00-P-067802 addressing this for M256, M276, and M278 engines. The repair involves resealing the covers with new gaskets and replacing the aluminium torque-to-yield bolts. Labor is approximately 3-4 hours. Additionally, the camshaft position sensor O-rings can leak, and if oil migrates along the wiring harness toward the ECU (the same wicking phenomenon known from the M278), repair costs escalate significantly. On the M256, this is less common than on the M278, but preventive replacement of camshaft sensor seals and installation of sacrificial pigtail harnesses is recommended. Simple reseal: €800-1,200 at an independent specialist. If oil has contaminated the harness: €1,500-2,500.

The 9G-TRONIC (725.0) 9-speed automatic is generally robust, but some W222 owners report torque converter shudder at low speeds, delayed engagement from park, or harsh low-gear shifts. Mercedes markets the transmission fluid as 'lifetime fill,' but real-world experience shows that proactive fluid and filter changes every 60,000-80,000 km significantly extend transmission life. A proper transmission fluid service costs €300-450. If the valve body solenoids have degraded, repair costs €1,200-2,000. Full mechatronic unit replacement or rebuild reaches €2,500-3,500. Catching shudder early and performing a fluid change with adaptation reset often resolves mild symptoms.

The W222 has numerous always-on monitoring systems (alarm, telematics, keyless entry receivers) that continuously tax the 12V battery. If the car sits for more than 7-10 days without being driven, the battery can be completely depleted. The Mercedes Me app typically shows a low-battery warning after about one week. The 12V AGM battery itself costs €200-350 to replace. A battery tender (CTEK MXS 5.0 recommended) is essential for cars that are not driven daily. If parasitic drain exceeds normal levels, diagnosing the source requires a specialist with Mercedes Star diagnostics, costing €100-200 in diagnostic time. Software updates have addressed some drain issues on specific production batches.

The W222 facelift uses the COMAND NTG5.5 infotainment system with a 12.3-inch display. Some owners report intermittent screen freezes, spontaneous reboots, and on earlier facelift production, internal screen delamination where the layers visibly separate. A software reset or update at a dealer can resolve freezing issues (€100-200 diagnostic fee). If the display itself is faulty, a refurbished replacement unit from Mercedes costs approximately €1,200-1,500 fitted. Aftermarket repair services can refurbish the existing screen for €500-800. Full new COMAND head unit replacement at a dealer can reach €2,000-2,500.