BMW M135i F40 Maintenance Guide

BMW M135i F40 Maintenance Guide

Maintenance Guide for the M135i F40

The BMW M135i F40 is a high-performance vehicle built for enthusiasts who value a balance of daily drivability and spirited performance. Maintaining your M135i properly is essential to ensure it remains reliable, safe, and fun to drive. This guide outlines BMW’s recommended service intervals and offers tips for owners who have modified their cars.

BMW-Recommended Service Intervals

BMW provides a flexible service schedule for the M135i F40, which may vary slightly based on driving conditions and usage. Below are the key service points:

Oil and Filter Change

  • Interval: Every 10,000 miles (15,000km) or annually, whichever comes first.
  • Use high-quality BMW approved oil - Check it out here

Brake Fluid Replacement

  • Interval: Every 2 years.
  • Use DOT 4 brake fluid. BMW recommends only approved fluids to ensure optimal performance.

Air Filter Replacement

  • Interval: Every 20,000 miles or as indicated by the vehicle’s condition-based monitoring system.
  • In dusty or harsh environments, inspect and replace the filter more frequently.
  • You could also opt for a performance "drop-in" filter as listed in our M135i Intake section

Cabin Air Filter

  • Interval: Every 10,000 miles (15,000km) or annually.
  • Ensures clean air inside the vehicle and prevents HVAC system issues.

Spark Plugs

Transmission Fluid (Automatic)

  • Interval: BMW claims their transmissions are “lifetime filled,” but it’s often recommended to replace the fluid around 40,000 to 60,000 miles for longevity, especially under heavy use.
  • If your gearbox feels "slow" or notchy in any way, replacing the fluids may resolve this problem

Coolant

  • Interval: Every 4 years.
  • Use BMW-approved coolant to prevent corrosion and overheating.

Differential Fluid

  • While BMW does not list a specific interval for the M135i’s all-wheel-drive system, changing the differential fluid every 50,000 miles is advisable for long-term performance.

Maintenance Tips for Modified M135i F40 Owners

Many M135i owners choose to modify their vehicles for added performance or personalization. Modifications can impact maintenance needs, so it’s essential to adapt your upkeep practices accordingly.

Engine Tune or ECU Remap

  • Oil Changes: If you’ve increased the engine’s output, shorten the oil change interval to 5,000–7,000 miles (10,000km)
  • Monitoring: Use tools to monitor critical parameters like oil temperature, boost pressure, and air-fuel ratios.

Aftermarket Air Intakes

  • Filter Cleaning: Clean and re-oil aftermarket filters every 10,000 miles or as recommended by the manufacturer.
  • Heat Management: Ensure proper heat shielding to avoid performance drops or engine damage.

Exhaust Modifications

  • Backpressure Monitoring: If you’ve installed a downpipe or cat-back system, ensure there’s no excessive backpressure that could damage the turbocharger.
  • Emission Systems: Be mindful of local regulations and ensure any changes comply with emissions laws.

Suspension Upgrades

  • Alignment: Check alignment regularly, especially if lowering springs or coilovers are installed. Improper alignment can cause premature tire wear.
  • Bushing Wear: Stiffer setups may accelerate wear on bushings and mounts, requiring more frequent inspection.

Track Use

  • Fluids: Use higher-grade brake fluid to prevent fade during track use. Engine oil and transmission fluid may also require more frequent changes. Motul RBF600 or Motul RBF660 is a great upgrade
  • Tires and Brakes: Inspect tires and brake pads after every track session, as these components wear faster under high loads. Check out our recommendations for upgrading your brakes here

General Maintenance Tips

  1. Condition-Based Monitoring (CBM): Utilize the vehicle’s CBM system to stay ahead of maintenance needs. BMW’s onboard diagnostics provide reminders for oil changes, inspections, and more.
  2. Battery Maintenance: The M135i’s electrical systems rely on a healthy battery. Keep it charged, especially in colder months or if the car isn’t driven frequently.
  3. Wash and Protect: Regularly wash your car, especially in winter, to remove salt and prevent corrosion. Use ceramic coatings or high-quality wax to protect the paint.
  4. Keep Records: Maintain detailed records of all services and modifications. This can help with troubleshooting and preserve resale value.

Conclusion

Proper maintenance of the M135i F40 is essential for enjoying its performance and reliability. Adhering to BMW’s service intervals while adapting your maintenance schedule for any modifications will keep your car in excellent condition. By staying proactive, you can maximize the lifespan and performance of your M135i while ensuring every drive is as enjoyable as the first.

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