Mercedes-Benz AMG G 65
Hand-built in Affalterbach to the One Man, One Engine principle — plaque with signature on the cam cover. Architecture: two separate six-cylinder banks, SOHC, three valves per cylinder (2 intake, 1 exhaust), derived directly from the M120 V12. 1,000 Nm from 2,300 rpm, electronically limited — the actual mechanical torque is estimated at 1,200 Nm. Dual ignition with 24 spark plugs, four catalytic converters (one pre-cat and one main cat per bank). At idle at 600 rpm virtually vibration-free — a deep, silky rumble. At full throttle a baritonal-metallic hiss that expands into a roar. No turbo lag: the torque plateau is so wide that boost build-up is barely perceptible. At 130 km/h the engine turns at approximately 1,700 rpm. 12.7 litres of oil capacity, major service from 1,500 EUR, 24-plug change from 900 EUR. ABC system overhaul can run into five figures. Maintained properly, one of the most effortlessly capable powerplants available.
V12 BiTurbo in a Military Box — Maximum Absurdity
Van-like aerodynamics, solid axles, military-derived ladder frame — and 630 hp with 1,000 Nm. 2.6 tonnes to 100 km/h in 5.3 seconds. At high speed the G becomes nervous and follows ruts, but that is not the point. The point is: 1,000 Nm from a box that has looked the same since the 1970s. Consumption beyond 20 litres guaranteed.
Engine Weaknesses 12
The M279 uses two fully potted ignition module banks for six cylinders each. Not repairable — replacement only. Failure documented from 60,000–100,000 km. Labour time is high due to tight packaging in the V-valley.
Symptoms: Misfires on one cylinder bank, rough running, power loss, check engine light with ignition fault code.
Both turbochargers wear at their bearing surfaces at high mileage. Replacing both turbos on the V12 requires extensive disassembly. Parts and labour costs run into five figures.
Symptoms: Metallic whine under load, oil loss at turbo mounting, power drop, blue smoke at full throttle.
The oil cooler sits centrally in the V-valley between the cylinder banks. The gasket becomes brittle under temperature cycling. Complete failure risks oil-coolant emulsification and overheating. Access is labour-intensive due to intake system removal.
Symptoms: Oil weeping visible in V-valley, possible oil-coolant emulsion on dipstick, oil smell after engine shutdown, coolant discolouration.
The Active Body Control system hydraulic lines become brittle over time. Leaks at fittings and line ends cause hydraulic fluid loss. Oil on hot components creates a fire risk.
Symptoms: Hydraulic fluid under the vehicle, uneven ride height, ABC warning in the instrument cluster.
The ABC hydraulic pump and valve block wear at high mileage. On the SL65 the pump alone takes around 13 hours to remove. A full system overhaul comes to €10,000–15,000.
Symptoms: ABC visit workshop warning, vehicle drops on one or all corners, stiffer suspension, hydraulic fluid loss.
The camshaft adjuster solenoids can leak. Oil migrates through the wiring harness to the ECU. A creeping defect: first cold-start rattle, later ECU failure.
Symptoms: Rattle on cold start that fades after a few seconds, rough running during warm-up, camshaft fault codes.
The gearbox was electronically limited to 1,000 Nm — the actual engine torque is higher. Torque converter and AMG-specific TCU wear under this constant load. Shift times under 100 ms stress the mechanicals.
Symptoms: Delayed pull-away, jerky gear changes, transmission warning, limp mode.
The stock plastic bypass valves on the compressor covers become leaky over time. Power loss and audible hissing result. Metal replacements are available and recommended.
Symptoms: Hissing on lift-off, power drop under higher load, rough running during boost build-up, boost pressure regulation fault codes.
Mercedes defines 1 litre per 1,000 km as normal for AMG engines. With the V12's 12.7-litre oil capacity and two turbochargers that can become relevant quickly. Valve stem seals and turbo shaft seals are the main culprits.
Symptoms: Dropping oil level between service visits, faint oil-burn smell after motorway runs, occasional blue smoke on cold start.
The hydraulically damped engine mounts harden at higher mileage. On the SL65, the replacement involves up to 25 hours of labour due to a different mounting arm design. Considerably simpler on the S/CL (around 5 hours).
Symptoms: Noticeable vibrations at idle, clunking under load changes, structure-borne noise in the cabin at low revs.
The V12 has two separate six-cylinder banks with numerous sealing surfaces. Valve cover gaskets start leaking from 80,000 km. Oil drips onto the hot exhaust — fire smell and smoke possible.
Symptoms: Oil smell after engine shutdown, oil mist in engine bay, oil drops under vehicle, burning smell from oil on exhaust.
The M279 uses twin-spark ignition with two plugs per cylinder — 24 in total. Replacement interval 60,000–90,000 km. Standard workshops often forget the second row. In cramped engine bays (S-Class, G-Class) accessibility significantly increases labour time.
Symptoms: When overdue: power drop, excess consumption, rough running, misfires on individual cylinders.
Vehicle Weaknesses 7
The W463 rusts structurally at window frames (not painted inside from the factory), lower door edges and sills. This problem runs through all model years up to 2018.
The steel ladder frame corrodes at spring seats and cross-members. The double-shell construction is insufficiently sealed and traps moisture.
Window frames are not painted on the inside from the factory and rust heavily. Tailgate and frame sections rust due to missing factory treatment. Full rust treatment up to 7,600 EUR.
Shock absorbers, springs and track rod ends wear out prematurely due to off-road use and the vehicle's high weight.
Worm gear in the steering box shows highest wear in the straight-ahead position. Steering levers and track rod ends are disproportionately often flagged at inspection.
ECU failures often only fixable by complete replacement. Older vehicles with moisture in the engine bay particularly affected. Specialist workshops offer cheaper repair options.
Moisture frequently enters headlights and tail lights, causing short circuits and bulb failures. Tail lights with poor factory sealing are particularly affected.