S68 Engine

BMW S68 4.4 V8 Bi-Turbo: Experiences, problems, fuel consumption and maintenance – The last samurai?

Introduction: The successor to the legendary S63

The engine with the code name S68 is BMW’s answer to increasingly strict emission regulations, without giving up the soul of a V8 powerplant. Although it shares the 4.4-liter displacement with its predecessor (S63), the S68 is in many respects a completely new engine. It is installed in the facelifted (LCI) versions of the BMW X5 M and X6 M Competition, as well as in the monumental XM. Its key feature is the integration of a 48-volt mild hybrid system directly into the gearbox, which makes it more technologically advanced but also more complex to maintain. This is probably the last new V8 engine to come out of the M division.

Technical specifications

Parameter	Data
Engine code	BMW S68
Displacement	4395 cc (4.4 L)
Configuration	V8, Twin-Turbo (Hot Vee)
Power	460 kW (625 hp)
Torque	750 Nm
Injection system	Direct injection (High Precision Injection)
Hybrid system	48V Mild Hybrid (electric motor integrated into the gearbox)
Camshaft drive	Chain

Reliability and maintenance

Timing system: Chain or belt?

The S68 uses a timing chain. BMW applied a similar architecture here as on previous V8 engines, with chains driving the camshafts. Although modern chains are more reliable than on the first-generation N63 engines, they still require top-quality oil and regular changes. A rattling sound on cold start is the first sign that the tensioners or the chain itself have given way, which requires immediate intervention.

Most common failures and what to watch out for

Since the engine is relatively new on the market, long-term data is still being collected, but based on its architecture and experience with similar “Hot Vee” engines, the following can be expected:

• Thermal management: Because the turbochargers are located between the cylinder heads, the temperature in that area is extreme. This leads to premature aging of rubber hoses, gaskets and plastic connectors in the cooling system. Coolant leaks into the “V” area are a classic problem.
• Cooling system: This vehicle has multiple radiators and electric water pumps. Failure of any pump can lead to overheating, which an aluminum block will not forgive.
• 48V system electronics: The integration of the electric motor and battery adds a layer of complexity. Software bugs or inverter issues can trigger the “Check Engine” light.
• Vanos solenoids: Sensitive to oil quality.

Service intervals and oil

A major service (chain replacement) is not strictly prescribed by mileage; it is done as needed (often around 150,000–200,000 km, but on M models it can be earlier due to driving style).

Minor service: Although the manufacturer recommends flexible intervals (up to 30,000 km), for this engine that is a death sentence. Change the oil at a maximum of 10,000 to 12,000 km.
Oil quantity and type: The S68 holds a large amount of oil, usually around 10.5 to 11 liters (depending on the exact oil pan variant; always check by VIN). The recommended grades are 0W-30 or 5W-30 with BMW Longlife-01 FE or Longlife-12 FE specification.

Oil consumption and spark plugs

Does it consume oil? Yes. High-performance V8 engines are designed with looser tolerances. Consumption of 0.5 to 1 liter per 2,000–3,000 km under aggressive driving is not unusual and does not necessarily indicate a fault. If it uses a liter per 500 km, then you have a problem (piston rings or valve stem seals).

Spark plugs: Due to direct injection and high turbo pressure, spark plugs wear out faster. The recommended replacement interval is every 30,000 to 40,000 km (often every second or third minor service).

Specific parts (costs)

Injection system and injectors

The S68 uses high-precision direct injection operating at pressures of up to 350 bar. The injectors are piezoelectric and extremely sensitive to poor fuel quality. Symptoms of problems include uneven idle, “stuttering” under acceleration or a smell of fuel from the exhaust. The price of a single injector is very high (varies by market).

Turbochargers, EGR and GPF

The engine has two twin-scroll turbochargers located in the middle of the V-block. Their service life directly depends on cooling. It is crucial not to switch off the engine immediately after hard driving.

This engine does not have a classic EGR valve like soot-prone diesels, but uses a variable valve timing system (Valvetronic/Vanos) for internal exhaust gas recirculation.
However, it is equipped with a GPF (Gasoline Particulate Filter). If the car is driven exclusively in city “stop-and-go” traffic, the GPF can clog, which chokes the engine and triggers a warning light on the dashboard. The solution is occasional highway driving at higher revs.
AdBlue: None, this is a petrol engine.

Fuel consumption and performance

Real-world consumption and city driving

Don’t be fooled by factory figures. This is a 2.4-ton beast with 625 horsepower.

• City driving: Expect between 16 and 22 l/100 km. In heavy traffic this can easily exceed 25 liters. The mild hybrid system helps a bit when setting off, but don’t expect miracles.
• Open road (up to 100 km/h): It is possible to get down to about 10–12 l/100 km if you are very gentle on the throttle.
• Motorway (130 km/h): Consumption is around 12–14 l/100 km.

Is the engine “lazy”?

Absolutely not. The word “lazy” does not exist in this engine’s vocabulary. With 750 Nm of torque available from just 1,800 rpm, the S68 catapults the heavy SUV as if it were a feather. The assistance of the electric motor (Mild Hybrid) eliminates even the small amount of “turbo lag” that could theoretically exist. Cruising at 130 km/h is done in 8th gear at very low revs (below 2,000 rpm), which makes the drive quiet and comfortable.

Additional options and modifications

LPG conversion

Is it suitable for LPG? NO. Although it is physically possible to install a liquid direct injection LPG system (LDI) for direct-injection engines, on this engine that is a technical sacrilege and a risk. The complexity of the electronics, high thermal loads and injector sensitivity make LPG installation uneconomical and risky. You also lose boot space and disturb the vehicle’s balance.

Remapping (Stage 1)

This engine has enormous potential. A Stage 1 remap (software only) can safely raise power to 700+ hp and 850+ Nm. However, you should know that the new BMW engine ECUs are often locked by the factory and need to be sent abroad for unlocking (“Femto unlock”). Also, any remapping immediately voids the factory warranty, which is a huge risk with such an expensive vehicle.

Gearbox: M Steptronic

The S68 engine comes exclusively with an 8-speed M Steptronic automatic gearbox with Drivelogic. This is not a dual-clutch (DCT) gearbox, but a conventional automatic with a torque converter (based on the ZF 8HP), specifically modified for M models.

Gearbox failures and maintenance

This is one of the best gearboxes in the world. It is robust and fast.

• Failures: Very rare if the gearbox is not overheated (e.g. too many consecutive Launch Control starts). The integrated electric motor is a novelty, so its long-term durability remains to be seen, but ZF rarely makes mistakes.
• Dual-mass flywheel: This model does not have a classic dual-mass flywheel like manual gearboxes or older DSG units. Instead, it uses a hydraulic torque converter (wandler) that dampens vibrations. The cost of replacing the converter is very high (expensive).
• Gearbox service: Although BMW often states that the oil is “lifetime”, the gearbox manufacturer (ZF) recommends changing the oil and filter (integrated into the gearbox pan) every 60,000 to 80,000 km. This is mandatory if you want the gearbox to last.

Used car purchase and conclusion

Buying a used X5 M or X6 M with the S68 engine requires caution. It is essential to check:

1. Cold start: Listen for chain rattle or metallic noises during the first 3–5 seconds.
2. Signs of leaks: Open the bonnet and look for white traces of dried coolant around the reservoirs and deep in the engine bay.
3. Exhaust smoke: Bluish smoke under sudden acceleration or after idling indicates oil consumption (turbos or valve stem seals).

Who is this engine for?

The S68 engine is intended for buyers who want uncompromising performance in an SUV format and for whom fuel, registration and maintenance costs are no issue. This is a status symbol and probably the pinnacle of ICE technology before the full switch to electric. If you are looking for economy, look at the diesel (B57). If you want emotion, sound and sheer force, the S68 is the right choice.