2017 MERCEDES-BENZ SL65 AMG

Typical onset: 30,000-70,000 mi

Symptoms: Sudden knocking or rattling from engine under load, Metal shavings in oil during change, Loss of oil pressure warning, Complete engine seizure in worst cases

Fix: This is the M279's Achilles heel—bearing shells can spin or fail, scoring the crank journals. If caught early with just noise, you're looking at bearing replacement with crank polish (engine-out, 25-30 hours). If it grenades, expect full short block or complete engine rebuild with new pistons, rings, crank, bearings—basically everything. Some owners go straight to AMG reman engine. 35-50 hours labor for full rebuild.

Estimated cost: $15,000-45,000

Typical onset: 50,000-90,000 mi

Symptoms: Vehicle sagging on one corner after sitting, ABC warning light with 'Vehicle too low' message, Hydraulic fluid puddles under car, Rough ride or loss of adaptive damping

Fix: ABC struts develop seal leaks, and the hydraulic lines corrode at fittings. Front struts are 8-10 hours each, rears are 6-8 hours. ABC pump failures also happen—add 12 hours. Mercedes fluid is mandatory ($40/quart, system holds 7+ quarts). This isn't if, it's when.

Estimated cost: $3,500-8,000

Typical onset: 60,000-100,000 mi

Symptoms: Transmission fluid pooling under engine bay, Burnt smell after highway driving, Harsh or delayed shifts when hot, Low transmission fluid warnings

Fix: The 7-speed MCT (multi-clutch transmission) oil cooler lines and cooler itself crack or seep. Cooler replacement requires partial front-end disassembly and is about 6-8 hours. Lines can be done separately at 3-4 hours. Use only MB-spec ATF.

Estimated cost: $1,800-3,200

Typical onset: 70,000-120,000 mi

Symptoms: Check engine light with underboost codes (P0299, P003A), Loss of power above 3,000 RPM, Turbo whistle or flutter under acceleration, Limp mode activation

Fix: The electronic wastegate actuators on these turbos stick or fail. Sometimes you can replace just the actuator (4-6 hours per side), but often the turbos need rebuild or replacement. Turbos are buried—figure 12-16 hours for both if you're doing full units. Not as common as bearing failure but still a V12-specific headache.

Estimated cost: $3,000-9,000

Typical onset: 80,000-130,000 mi

Symptoms: Rough idle or misfires on cold start, Multiple misfire codes (P030X), Reduced fuel economy, Hesitation during acceleration

Fix: Direct injection means carbon deposits, and this V12 has 12 piezo injectors that can clog or fail electrically. Walnut blasting the intake ports is 8-10 hours. Injector replacement on a V12 is 10-14 hours due to valley access. Injectors are $300-500 each from Mercedes—do all 12 if budget allows.

Estimated cost: $4,000-8,500

Typical onset: 40,000-80,000 mi

Symptoms: Clunk when shifting from Park to Drive, Vibration through chassis at idle, Excessive driveline movement visible during throttle blips

Fix: Hydraulic transmission mounts collapse, especially the rear trans mount. It's a 3-4 hour job to replace both engine and trans mounts. Not a safety issue but very annoying in a $250k car. OEM mounts only—aftermarket don't hold up.

Estimated cost: $1,200-2,000