S63B44B Engine

S63B44B (BMW M5 CS) – Experiences, Issues, Fuel Consumption and Used-Buying Guide

If you’re looking for the pinnacle of Bavarian engineering in the modern era, the S63B44B in its most powerful iteration (installed in the M5 CS) is exactly that. This is not an ordinary engine; it’s the heart of a supercar trapped in a sedan body. Although it shares the basic architecture with standard V8 engines, the version in the M5 CS is tightened to the absolute limit, with a forged crankshaft, an upgraded cooling system and turbochargers that run at enormous boost pressures. However, owning such a machine requires a budget not only for the purchase, but also for meticulous maintenance.

Key points in short (TL;DR)

• Unmatched performance: With 635 hp, this is one of the most powerful production BMW engines ever.
• Hot-V configuration: The turbochargers are placed inside the V of the engine for better response, which creates extreme temperatures.
• Oil consumption: Expect to top up oil between services – this is a “factory feature” of these engines.
• Cooling system maintenance: Plastic hoses and connectors are prone to cracking due to the high heat in the engine bay.
• No manual gearbox: It comes exclusively with the top-tier ZF 8-speed automatic.
• Not made for city traffic jams: Although it can be driven in the city, the engine suffers (soot buildup, overheating of components) if it doesn’t get “blown out” on open roads.
• Expensive maintenance: Parts are specific to the M division and prices are significantly higher than for standard BMW models.

Contents

• Technical Specifications
• Reliability and Maintenance
• Specific Parts (Costs)
• Fuel Consumption and Performance
• Additional Options and Modifications
• Transmission
• Buying Used and Conclusion

Technical Specifications

Feature	Data
Engine code	S63B44B (S63TU4 specification)
Displacement	4395 cc (4.4 L)
Power	467 kW (635 hp)
Torque	750 Nm
Configuration	V8, Twin-Turbo (Hot-V)
Injection	Direct injection (High Precision Injection)
Camshaft drive	Chain

Reliability and Maintenance

Over the years, BMW’s S63 engine has overcome many of the “childhood diseases” of its predecessor (the N63), but it is still a very complex machine. In the M5 CS, this engine operates under enormous stress and requires an owner who does not skimp on preventive maintenance.

Camshaft drive (Timing chain)

This engine uses a timing chain. Although it is designed to last the entire service life of the vehicle, in practice, due to the enormous torque and frequent aggressive launches, the chain can stretch. The critical mileage is usually around 150,000 km, but on such a powerful engine, any “rattling” noise at cold start should be taken seriously even earlier. Replacing the chain on the S63 is a very expensive and labor-intensive job that often requires removing the engine.

Most common failures

The Achilles’ heel of this engine is the cooling system and heat management. Due to the “Hot-V” configuration (where the turbochargers are placed between the two banks of cylinders), the temperature in that area is extreme. This leads to:

• Cracking of plastic and rubber coolant hoses: The materials become brittle and crack, which can cause a sudden loss of coolant.
• Oil leaks: Valve cover and oil pan gaskets often start leaking before 100,000 km.
• Injector issues: If an injector “sticks open”, it can wash the oil film off the cylinder wall and cause catastrophic engine damage. Symptoms include a smell of fuel in the oil and rough running.
• Ignition coils: They often fail due to heat, causing misfires.

Service intervals and oil

Forget about “Long Life” 30,000 km intervals if you want this engine to last. An oil service must be done every 8,000 to 10,000 km at most, or once a year.

The engine takes a huge amount of oil – approximately 10 to 10.5 liters (always check the exact specification by VIN, as the M5 CS has a specific oil pan). The use of high-quality synthetic oil with a viscosity grade of 0W-30 or 5W-30 (BMW LL-01 or LL-04 specification) is recommended, although many enthusiasts switch to 5W-40 for better protection at high temperatures.

Oil consumption

Yes, this engine consumes oil and that is completely expected. High-performance twin-turbo V8 engines have looser tolerances. Consumption of 1 liter per 2,000 to 3,000 km is considered acceptable, and even normal with more aggressive driving. Always keep a liter of oil in the trunk.

Spark plugs

In the M5 CS, the spark plugs are under heavy stress. It is recommended to replace them every 30,000 km (every third oil service). If the engine is tuned (chipped), this interval should be cut in half.

Specific Parts (Costs)

Turbochargers

The engine has two twin-scroll turbochargers placed in the V of the engine. Their lifespan depends directly on the driving style and how the car is shut down. If the car is turned off immediately after hard pulls on the highway, the oil in the turbos will coke and they will fail. With proper cooldown (idling for a minute or two before shutting off), they can last over 150,000 km. Overhaul or replacement is a very expensive operation (depends on the market).

Fuel injection system

It uses high-pressure piezo-electric direct injection. The injectors are sensitive to poor fuel quality. Problematic injectors manifest as hesitation under acceleration, smoke from the exhaust, or a rising oil level (fuel in the oil pan). A new set of injectors is a costly expense.

DPF / GPF / EGR

Since this is a petrol engine, there is no DPF filter. However, models for the European market (including the M5 CS) are equipped with a GPF (Gasoline Particulate Filter), which is the petrol equivalent of a DPF. It also has catalytic converters. The GPF rarely clogs unless the car is driven exclusively on short city trips, which is not typical for this kind of car. There is no AdBlue system.

Fuel Consumption and Performance

Real-world fuel consumption

If you’re asking about fuel consumption, this is probably not the car for you, but here’s the reality:

• City driving: Expect between 16 and 22 l/100 km. In heavy traffic it can go over 25 liters.
• Open road (highway): At a steady 130 km/h, thanks to the long 8th gear, consumption can drop to a surprising 10–11 l/100 km.
• Aggressive driving: The sky’s the limit (30+ l/100 km).

Is the engine “lazy”?

Absolutely not. With 635 hp and 750 Nm available from as low as 1,800 rpm, this engine catapults the heavy M5 body. The M5 CS accelerates from 0 to 100 km/h in 3.0 seconds (often even quicker in practice). The sensation of power is brutal and instantaneous.

On the highway

This is the natural habitat of this engine. At 130 km/h the engine is “sleeping” at a low ~1,800–2,000 rpm in 8th gear. Sound insulation is top-notch, and the power reserve for overtaking is available in milliseconds.

Additional Options and Modifications

LPG (autogas) conversion

Absolutely not. Technically, there are systems for direct liquid gas injection that could work, but installing LPG on a limited-run model like the M5 CS is heresy. On top of that, the complexity of the electronics and the sensitivity of the engine make this an extremely risky move that will certainly destroy the car’s value and potentially damage the engine.

Chiptuning (Stage 1)

The S63 engine has enormous potential. With software tuning alone (Stage 1), power can easily be raised to 700+ hp and 850+ Nm. However, keep in mind that the M5 CS is already heavily “wound up” and optimized from the factory. Further power increases put additional stress on the connecting rods and the transmission. The recommendation is to leave the CS model in stock condition because of its collectible value.

Transmission

In the M5 CS (F90), this engine comes exclusively with the 8-speed M Steptronic automatic transmission with Drivelogic. This is essentially a tuned version of the legendary ZF 8HP gearbox.

Reliability and failures

This is one of the best transmissions in the world. It is very reliable and durable, capable of handling enormous torque. It has no typical inherent issues. Failures are rare and usually the result of lack of maintenance or extreme tuning.

Dual-mass flywheel and clutch

This transmission is a conventional automatic with a torque converter, so it does not have a clutch kit and dual-mass flywheel in the sense that manual or DSG gearboxes do. However, there is a vibration damper which is part of the converter. Replacing it is expensive, but rarely needed before very high mileage. There is no “clutch” cost here as part of regular maintenance.

Transmission service

Although BMW often states that the transmission oil is “lifetime fill”, the transmission manufacturer (ZF) recommends changing the oil and filter (integrated into the transmission pan) every 80,000 to 100,000 km, or earlier with aggressive driving. The oil change costs a moderate amount (depends on the market), but is crucial for longevity.

Buying Used and Conclusion

When buying an M5 CS with the S63 engine, a visual inspection is not enough. Be sure to:

• Listen to a cold start: Any chain rattling in the first 3–5 seconds is a red flag.
• Check for signs of leaks: Remove the plastic engine cover and use a flashlight to inspect the “V” area between the cylinder banks – coolant collects there if hoses are leaking.
• Run diagnostics: Checking injector corrections and the history of misfire codes is mandatory.
• Watch the exhaust smoke: Bluish smoke under sudden throttle or after idling indicates oil consumption (valve stem seals or turbochargers).

Conclusion: The S63B44B in the M5 CS is a masterpiece. It is not an engine for everyone. It is intended for enthusiasts who understand that top-tier performance requires top-tier (and expensive) maintenance. If you are ready to “feed” this beast with fuel and quality parts, you will get one of the best driving experiences money can buy. If you are looking for the economy and reliability of a Toyota – skip it.