BMW M5 Touring
The S68B44 is BMW's most complex M engine to date: 4.4-litre V8 twin-turbo coupled to a 48V mild hybrid system, up to 727 hp system output in the G90 M5. The hybrid isolation takes some of the V8 character — silent in EV mode, in Sport mode a muted V8 growl that never reaches the rawness of an S62 or the sharpness of an S85. The power delivery is brutally linear: no turbo lag, no hesitation, but also no climax in the rev band — thrust from bottom to top, full stop. 2,450 kg kerb weight cannot be argued away: in tight corners, under braking, on turn-in — the weight is always there. The 14.8 kWh battery enables around 40 km of EV range for everyday use, which drastically reduces consumption. Oil changes every 10,000 km; cooling circuit complexity (combustion engine + electric motor + battery + gearbox = 4 separate circuits) becomes a cost factor at higher mileages.
2.5-tonne estate with 727 hp — absurd, but honest
The M5 Touring G99 is what happens when you build an estate car with supercar power and then put in 400 kg of battery. Frighteningly fast on the motorway, too heavy on a back road for real driving pleasure. As an all-round weapon for families who want to do 300 km/h — unmatched. As a sports estate — too fat.
Engine Weaknesses 7
The twin-scroll turbochargers of the S68B44 are designed for high sustained output in M mode, but react sensitively to inadequate oil supply. Frequent full-load driving without a cool-down phase significantly increases bearing risk.
Symptoms: Whistling under acceleration, blue exhaust smoke, power drop, oil pressure warning.
The S68B44 combines V8 turbo heat with 48V hybrid electronics waste heat. The multi-zone cooling system with separate circuits for engine, battery and electronics is complex. Under sustained full load on a track, power reduction can be activated.
Symptoms: Thermal throttling (limp mode) after extended full-load phases, coolant temperature warning, PHEV system deactivates to protect itself, excessive cooling fan noise.
First BMW M engine with a mild hybrid system. Isolated reports of faults in the 48V system and boost recuperation. Model still too new for established patterns.
Symptoms: Warning messages in instrument cluster, boost function unavailable, unexpected restart
The S68B44 shows increased oil consumption with spirited driving and high engine loads, typical of BMW V8 turbo engines. Valve stem seals and crankcase ventilation are the main causes at higher mileages.
Symptoms: Oil level drops faster than expected, faint blue smoke under high load, oil warning light.
The 48V mild hybrid system integrated into the ZF eight-speed gearbox of the S68B44 is still new to market. Integrity issues with the high-voltage electronics and ISG module can trigger unexpected shutdowns.
Symptoms: Hybrid system warning in instrument cluster, boost function disabled, occasional restricted mode.
The integrated starter-generator (ISG) of the 48V mild hybrid system is a highly loaded mechanical-electrical component. With aggressive use, the ISG bearings and belt can wear prematurely.
Symptoms: Hybrid system warning light, boost function unavailable, faint rattling from the gearbox area under acceleration, unexpected cut-out of electric assist.
The 14.8 kWh high-voltage traction battery degrades over time — especially with frequent fast charging or temperature extremes. Loss of more than 20% capacity noticeably reduces electric range and boost performance.
Symptoms: Shortened electric range (under 20 km instead of 45+ km), reduced boost, longer charging times, battery warning messages in iDrive.
Vehicle Weaknesses 6
BMW recalled G90 M5 vehicles because an incorrectly routed cockpit wiring harness can be damaged during cabin filter replacement. Short circuit can lead to fire. KBA 16187R.
The M5 G90 weighs around 2,435 kg as a PHEV — approximately 500 kg more than the predecessor F90. In tight corners the car pushes over the front wheels. The PHEV system is still very young; long-term data is lacking.
Related BMW PHEV models (X5 50e) show CCU (Combined Charging Unit) failures at under 2,000 km. Whether the M5 G90 uses identical parts remains open — the model is too young for reliable data.
An incorrectly manufactured double universal joint in the steering spindle can break and lead to stiff or jerky steering. KBA 14353R.
The additional weight of approximately 500 kg compared to the F90 M5 puts significantly more stress on the brakes. Despite regenerative braking, the mechanical brakes need replacing sooner than the predecessor.
The PHEV system of the G90 M5 brings around 400 kg of additional weight. Despite adaptive suspension, the damping remains suboptimal over sharp bumps.