The BMW S85 engine, a naturally aspirated 5.0-liter V10, stands as one of BMW M’s most ambitious engineering feats. Developed for the E60 M5 and E63/E64 M6, the S85 was inspired by BMW’s Formula 1 expertise in the early 2000s, showcasing a high-revving design, incredible sound, and motorsport technology. While revered by enthusiasts for its performance and character, the S85 also comes with a reputation for high maintenance demands and potential reliability concerns. This article dives into the S85’s pros, cons, reliability, tuning potential, and maintenance needs.

Pros of the S85 Engine

  • The S85 produces 500 horsepower at 7,750 RPM and 384 lb-ft of torque at 6,100 RPM.
  • With an 8,250 RPM redline, the engine delivers thrilling high-revving performance, making it a standout in its class.
  • Borrowing from BMW’s Formula 1 expertise, the engine features advanced materials and technology, including individual throttle bodies and a lightweight design.
  • The S85 delivers a unique exhaust note, often described as one of the best in BMW history, blending a high-pitched wail with a deep growl.
  • As BMW’s only production V10 engine, the S85 holds a special place in the brand’s history and offers a unique driving experience.

Cons of the S85 Engine

  • The S85 is prone to several issues, including rod bearing wear, VANOS solenoid failure, and throttle actuator problems.
  • High oil consumption is common, particularly as the engine ages.
  • The advanced design and intricate components make the S85 difficult and expensive to repair and maintain.
  • Diagnostic and repair work often requires specialized knowledge and tools.
  • Most S85-equipped cars were paired with the SMG III single-clutch automated manual transmission, which is known for jerky shifts and frequent hydraulic pump failures.
  • Routine maintenance and potential repairs can be prohibitively expensive, with rod bearing replacements and VANOS repairs being particularly costly.
  • The engine’s high-strung nature and fuel consumption make it less practical for daily driving, with average mileage often in the single digits.

Reliability of the S85 Engine

The S85’s reliability is often debated. While many owners enjoy trouble-free experiences with proper maintenance, others face significant issues due to neglect or design flaws. Key concerns include:

  • Rod Bearings: Premature rod bearing wear is one of the most well-known issues. BMW’s original bearings and oil clearances were insufficient for the high-revving design, requiring replacements every 60,000–80,000 miles.
  • Throttle Actuators: The electronic throttle actuators can fail due to worn gears, leading to limp mode. Replacements are common at higher mileages. Some owners report early wear and tear on those.
  • VANOS System: The dual VANOS system is prone to solenoid failure, which can result in rough idle, loss of power, or check engine lights.
  • Cooling System: Cooling system components, including the water pump and thermostat, often fail prematurely, risking engine overheating.
  • SMG Hydraulic Pump: Owners noticed occasional hesitation during shifts occurred when the motor struggled to build hydraulic pressure quickly enough.
  • Serpentine Belt

Models Using The S85 Engine

  • 2005–2010 E60/E61 M5
  • 2005–2010 E63/E64 M6
  • 2009–2010 Wiesmann GT MF5
  • 2009–2013 Vermot Veritas RS III

Tuning the S85 Engine

The S85 offers considerable tuning potential, though its naturally aspirated design limits gains without significant modifications.

  • ECU Tuning: Software tunes can optimize throttle response, remove the speed limiter, and refine power delivery, typically adding 10–20 horsepower.
  • Exhaust Systems: Upgrading the exhaust can unlock a more aggressive sound and minor performance gains, particularly with headers or catless setups.
  • Forced Induction: Supercharging is a popular route for those seeking substantial power increases. Aftermarket kits can push output beyond 700 horsepower, but require significant investment and supporting modifications.
  • Weight Reduction: Since the S85 is already highly optimized, performance improvements can also come from reducing vehicle weight rather than engine upgrades.
  • Intake Modifications: Carbon fiber airboxes and high-flow filters can improve airflow and enhance the engine’s induction noise.

Maintenance Tips for the S85 Engine

  • Rod Bearing Replacement: Proactively replace rod bearings to prevent catastrophic engine failure. Consider upgraded bearings with improved clearances and high-performance oil.
  • Oil Changes: Use high-quality synthetic oil (10W-60 is recommended) and change it every 5,000 miles to minimize wear.
  • VANOS Maintenance: Regularly inspect and replace VANOS solenoids and seals as needed to maintain optimal performance.
  • Throttle Actuator Replacement: Monitor throttle actuators for signs of failure and replace them with upgraded units when necessary.
  • Cooling System Overhaul: Replace the water pump, thermostat, and hoses at regular intervals to prevent overheating.
  • Transmission Care: If equipped with the SMG transmission, service the hydraulic system and consider converting to a manual gearbox for improved reliability and driving enjoyment.
  • Regular Diagnostics: Perform regular diagnostics to catch potential issues early. A reliable OBD scanner or BMW-specific diagnostic tool is essential.

The BMW S85 engine is a true engineering achievement, delivering exceptional performance, an unforgettable soundtrack, and an exhilarating driving experience. However, its intricate design and high maintenance demands make it a challenging choice for ownership. With diligent care and regular upkeep, the S85 can provide years of thrilling performance, but potential buyers should be prepared for the associated costs and occasional repairs. For those who are passionate and ready to invest the effort, the S85 stands out as one of BMW’s most iconic engines, embodying the brand’s rich motorsport heritage.