2018 MERCEDES-BENZ S65 AMG

Typical onset: 40,000-80,000 mi

Symptoms: Metallic knocking or rattling at idle that worsens under load, Low oil pressure warnings despite proper oil level, Metal shavings or glitter in oil during changes, Sudden catastrophic failure with loss of power and grinding noises

Fix: Engine-out teardown reveals spun bearings—often rod bearings first, but main bearings follow. This necessitates complete short block replacement or full rebuild with crankshaft machining. 60-80 hours labor at specialty shop. Many owners opt for factory reman long block due to tight tolerances and hand-build nature of M279.

Estimated cost: $45,000-75,000

Typical onset: 50,000-90,000 mi

Symptoms: Excessive blue smoke on cold start or hard acceleration, Oil consumption exceeding 1 quart per 1,000 miles, Misfires on specific cylinders (typically banks that run hotter), Loss of compression detected during diagnostic testing

Fix: Rings lose tension or cylinder walls score due to inadequate lubrication or heat cycling. Requires engine removal, complete disassembly, bore inspection, possible sleeving, new pistons and rings. Often discovered alongside bearing issues. 70-90 hours labor plus machine work.

Estimated cost: $50,000-85,000

Typical onset: 60,000-100,000 mi

Symptoms: Transmission fluid spots under vehicle, often pink or red, Transmission running hotter than normal (over 220°F), Fluid level dropping between services, Rough shifting when trans is cold

Fix: The AMG Speedshift MCT 7-speed cooler lines and cooler itself develop seepage at crimp joints and internal failures. Cooler is integrated into radiator stack on some configurations. Replacement requires partial front-end disassembly. 6-9 hours labor depending on cooler location.

Estimated cost: $2,800-4,500

Typical onset: 50,000-80,000 mi

Symptoms: Clunking or thudding when shifting from Park to Drive/Reverse, Excessive vibration at idle, especially with A/C on, Visible sagging or cracking of rubber mount components, Drivetrain lash felt during throttle application

Fix: The hydraulic transmission mount fails from age and the stress of 738 lb-ft torque. Requires lift and support of transmission. OEM part is expensive but necessary—aftermarket doesn't handle the load. 3-4 hours labor.

Estimated cost: $1,200-1,800

Typical onset: 40,000-70,000 mi

Symptoms: Hesitation or stumbling under wide-open throttle, Limp mode activation with fuel pressure fault codes (P0087, P0088), Rough idle or extended cranking before start, Reduced power output at high RPM

Fix: The V12 runs a sophisticated high-pressure direct injection system sensitive to fuel contamination. Filter element is buried in tank module on some configurations or inline on chassis. Tank-drop jobs run 5-7 hours; inline replacements 2-3 hours. Always replace fuel if contamination suspected.

Estimated cost: $800-2,200

Typical onset: 60,000-100,000 mi

Symptoms: Rattling noise from engine bay on cold start that disappears when warm, Overboost or underboost fault codes (P0299, P0234), Inconsistent throttle response and power delivery, Check engine light with boost pressure deviations

Fix: Wastegate actuator arms wear or seize, and diaphragms leak. Twin turbos mean double the cost. Turbos require manifold removal; accessibility is nightmare on V12. Each turbo rebuild or replacement runs 12-16 hours labor due to packaging. Sometimes only actuators need replacing (6-8 hours).

Estimated cost: $8,000-18,000

Typical onset: 70,000-110,000 mi

Symptoms: "ABC Visit Workshop" warning on dash, Vehicle sits low on one or more corners, Groaning or whining noise from under hood during suspension movement, Harsh ride quality and loss of self-leveling function

Fix: The ABC system uses high-pressure hydraulics (3,000+ psi). Pump, accumulator spheres, and valve blocks all fail. Pump replacement is 4-6 hours; accumulators add another 2-3 hours each. Fluid flush mandatory after repairs. This system is brutally expensive—consider carefully if inactive on a used example.

Estimated cost: $4,500-9,000