BMW M5 vs AMG E63 S Reliability —The $15,000 Maintenance Trap

The battle between the BMW M5 and the Mercedes-AMG E63 S is the oldest and most fierce rivalry in the luxury sedan world. For the current generations—he F90 M5 and the W213 E63 S—oth manufacturers abandoned rear-wheel drive and deployed massive twin-turbo V8s mated to all-wheel-drive systems, resulting in 0-60 times under 3.0 seconds.

But paper specs don’t pay the mechanic. If you are cross-shopping these two used titans, you need to understand their completely different failure profiles. Which V8 super-sedan will bankrupt you faster?

Powertrain Reliability: The S63 vs The M177

Both the BMW and the AMG use a “Hot-V” engine configuration, where the twin turbochargers sit inside the valley of the engine block. This creates immense heat that eventually destroys surrounding components.

The BMW M5 (4.4L S63 V8)

The F90 M5 is the final iteration of the S63 engine. BMW fixed the catastrophic rod-bearing failures of the previous F10 generation, but the engine remains highly sensitive.

• The Weakness - Death by a Thousand Cuts: The M5 rarely suffers total engine failure anymore. Instead, it suffers from constant, expensive top-end maintenance. The immense heat bakes the plastic turbo coolant lines, the coil packs, and the spark plugs. The high-pressure fuel injectors are also prone to failing open.
• The Reality: You will be at the shop 3 times a year for $2,000 bills.

The AMG E63 S (4.0L M177 V8)

The AMG 4.0L V8 is mechanically brilliant. The block is derived from the AMG GT supercar and is physically stronger than the BMW’s block.

• The Weakness - The Massive Catastrophe: While the engine internals are strong, the Air-Oil Separator (AOS) and PCV system frequently fail. When this happens, crankcase pressure builds up instantly and completely blows out the Rear Main Seal (RMS). Because of the AWD system, fixing this tiny seal requires dropping the entire transmission and subframe.
• The Reality: You may only visit the shop once a year, but the bill will be $4,500+. Read our deep dive on Burning Oil Smells for more on RMS failures.

Transmissions: The Real Differentiator

This is where the reliability gap diverges sharply.

• BMW M5 (ZF 8-Speed Automatic): BMW ditched their clunky dual-clutch transmission for a traditional ZF torque-converter automatic. It is, without a doubt, the most reliable transmission in the luxury segment. Change the fluid at 50,000 miles, and it will last forever.
• Mercedes E63 S (AMG MCT 9-Speed): Mercedes uses a Multi-Clutch Technology (MCT) transmission. Instead of a torque converter, it uses a massive wet clutch pack. It allows for brutal launch control, but it is incredibly finicky. It is prone to violently harsh 3-to-2 downshifts, overheating, and total failure. Replacing the MCT transmission out of warranty pushes $15,000.

5-Year Ownership Cost Estimate (Assuming 40k Miles Driven)

If you buy a 4-year-old CPO model and drive it for 5 years, here is a realistic maintenance and repair budget:

BMW F90 M5:

• Routine Maintenance (Oil, Filters, Plugs): $4,000
• Brakes & Tires (2 Sets): $7,500
• Unscheduled Repairs (Coolant lines, Injectors): $6,000
• Total 5-Year Running Cost: ~$17,500

Mercedes-AMG W213 E63 S:

• Routine Maintenance: $4,500
• Brakes & Tires: $7,500
• Unscheduled Repairs (RMS, Suspension, MCT tweaks): $8,500
• Total 5-Year Running Cost: ~$20,500

Conclusion

The BMW M5 is mathematically the safer financial bet on the used market, largely due to its bulletproof ZF transmission. However, the E63 S feels significantly more aggressive and dramatic. If you can afford an exclusionary extended warranty, the AMG is the more exotic experience. Without a warranty, buy the BMW.