BMW S63 vs Mercedes M278: Performance vs Reliability
BMW S63 vs Mercedes M278: Performance vs Reliability
Reliability Score
Based on owner reports and frequency of repairs.
Published on: Sun Feb 15 2026
BMW S63 vs Mercedes M278: Performance vs Reliability
This is the battle of the titans. In one corner, the BMW S63. The M-Division’s high-revving athlete. In the other, the Mercedes M278 (and its AMG brother, the M157). The torque-monster cruiser.
They define the German V8 era of the 2010s. But if you are buying one out of warranty, you are playing with fire. Which fire burns slower?
1. The Design Philosophy
- BMW S63: Designed for the track. 7,200 RPM redline. Instant throttle response. Cross-bank manifolds. It is high-strung. It is always “on.”
- Mercedes M278: Designed for the Autobahn. 5,000 RPM shifts. Wave of torque. Conventional manifold. It is relaxed. It lumps along at 1,500 RPM.
Reliability Implication: The BMW wears out its bearings because of high RPM and G-forces. The Mercedes wears out its timing chains because of long chains and start-stop cycles.
2. The BMW S63: The Known Devil
We know exactly how the S63 dies.
- Rod Bearings: They wear out.
- Injectors: They stick open.
The Strategy: You can “bulletproof” an S63.
- Buy car.
- Spend $3,000 on bearings.
- Spend $3,000 on injectors.
- Result: You have a nearly unkillable 600hp engine for the next 60k miles.
3. The Mercedes M278: The Silent Assassin
The M278 (found in S550, E550, GL550) is generally seen as more reliable. “It’s a Benz V8, it lasts forever.” False.
It has two major flaws:
- Timing Chains: The tensioners fail. The check valves fail. The chain rattles on startup. If ignored, it jumps time. Repair: $4,000 - $6,000.
- Cylinder Scoring (Alusil): This is the killer. The Silitec coating on the cylinder walls degrades. The piston scuffs the wall.
- Symptom: Misfire on Cylinder 1 or 5. Low compression.
- Fix: None. You cannot re-sleeve an Alusil block easily. You need a new engine.
- Cost: $15,000 - $20,000.
The Risk: You cannot “prevent” cylinder scoring easily. It just happens on some engines.
4. Maintenance Comparison
| Item | BMW S63 | Mercedes M278 |
|---|---|---|
| Oil Change | $200 (Every 3k) | $200 (Every 5k) |
| Spark Plugs | $600 (Every 20k) | $400 (Every 50k) |
| Transmission | DCT ($800) | 7G-Tronic ($400) |
| Suspension | $2,000 (M-Tax) | $3,000 (Airmatic) |
| Check Engine Light | Frequent (Sensitive) | Rare (Stoic) |
Winner: Mercedes. It requires less attention… until it explodes.
5. Driving Experience
- BMW S63: It begs you to drive fast. The downshifts blip. The exhaust pops. It shrinks the car.
- Mercedes M278: It wafts. It has endless power, but it doesn’t shout about it. It makes the car feel substantial.
6. The Verdict: Which is Safer?
If you are a “Car Guy/Gal” who wrenches or has a good shop: BMW S63. Why? Because preventive maintenance works. You can fix the bearings. You can fix the injectors. You control your destiny.
If you are a “Normal Driver” who just wants a luxury car: Mercedes M278. Why? Because 90% of them run fine to 150k miles without scoring. It is a lower probability of failure, but a higher consequence (fatal engine damage) if it hits.
The Smart Money:
- Best: 2018+ BMW S63TU4 (F90 M5) - Reliable AND Fast.
- Good: 2015+ Mercedes M278 (Updated tensioners).
- Risky: 2012-2016 BMW S63TU (Unless bearings done).