2012 maintenance schedule
2012 BMW 135i Convertible Complete Maintenance Schedule & Service Guide
The 2012 BMW 135i Convertible is equipped with the Condition Based Service (CBS) system, a sophisticated maintenance monitoring approach that...
Last updated
September 15, 2026
Reviewed for service schedule clarity.
Key Takeaways
- The 2012 BMW 135i Convertible is powered by the N55 3.0-liter turbocharged inline-6 engine and is rear-wheel drive. It was sold with 48 months or 50,000 miles of free scheduled maintenance under BMW Ultimate Service, which has long since expired .
- The vehicle uses a Condition Based Service (CBS) system that monitors driving conditions to calculate personalized service intervals rather than applying fixed mileage to every item .
- BMW recommends spark plug replacement at 60,000 miles for the N55 engine; for modified or aggressively driven vehicles, a shorter interval is advisable .
- Brake fluid requires replacement every two years as a fixed time-based interval critical for braking system health .
- The N55 engine has an oil capacity of approximately 6.5 liters and requires BMW Longlife-01 approved synthetic oil .
Understanding the BMW Maintenance System
The 2012 BMW 135i Convertible is equipped with the Condition Based Service (CBS) system, a sophisticated maintenance monitoring approach that represents a departure from traditional fixed-interval schedules .
How CBS Works
Sensors and special algorithms evaluate the different driving conditions of your BMW to determine current and future service requirements . Your driving style, trip length, and operating conditions all influence when service becomes due.
On the Control Display or instrument cluster, you can view remaining times or distances for :
- Engine oil service
- Front and rear brake pads
- Brake fluid
- Vehicle check
- Legally mandated inspections depending on local regulations
Service Data in the Remote Control
Your vehicle continuously stores service-requirement information in the remote control while you are driving . Your BMW Service Advisor can read this data from the remote control unit and propose an optimized maintenance approach. Whenever you take your car in for servicing, you should hand your BMW Service Advisor the remote control unit that you last used .
Important: Make sure that the date is always set correctly; otherwise, the effectiveness of Condition Based Service CBS is not assured .
Factory Maintenance Schedule
The following represents verified OEM maintenance information for the 2012 BMW 135i Convertible based on BMW technical documentation and specialist sources.
Engine Oil Service
The CBS system determines engine oil change intervals based on driving conditions rather than a fixed mileage schedule. BMW suggests oil changes approximately every 10,000 miles or 12 months, depending on driving habits .
Oil Capacity: The N55 engine has an oil capacity of approximately 6.5 liters .
Oil Specifications: The N55 engine requires BMW-approved synthetic oils. BMW recommends oils meeting Longlife-01 specifications . Approved viscosity grades include SAE 5W-30 and 5W-40 .
Owner Guidance: For owners driving aggressively or with modifications, a shorter interval of 5,000 to 7,000 miles is recommended . This conservative approach is particularly advisable for the turbocharged N55 engine, which places greater thermal stress on engine oil.
Spark Plug Service
For the N55 engine in the 2012 135i, BMW recommends replacing spark plugs at 60,000 miles .
Owner Guidance: For modified vehicles or those with higher boost levels, consider replacing spark plugs every 30,000 to 40,000 miles, or even sooner if the car is used hard or on track . Replacing ignition coils as preventive maintenance when performing spark plug service is also recommended .
Brake Fluid Service
BMW mandates that brake fluid be replaced every two years . This is a fixed time-based interval critical for maintaining braking performance and preventing internal corrosion in the hydraulic system.
Owner Guidance: Consider upgrading to a superior brake fluid such as Castrol RBF600 or Castrol RBF660 for spirited driving .
Air Filter Replacement
BMW recommends replacing the engine air filter every 30,000 miles, with more frequent inspection if driving in dusty conditions .
Coolant Service
BMW recommends replacing the coolant every 4 years or 60,000 miles . Always use BMW-approved coolant to prevent corrosion and maintain cooling efficiency .
Vehicle Check
BMW specifies a comprehensive Vehicle Check as part of the maintenance schedule . This includes:
- Brake system connections and lines for leaks, damage, and correct positioning
- Underbody components including transmission, rear axle, fuel lines, and exhaust system
- Steering components for clearance, leaks, damage, and wear
- Road test with checks of brakes, steering, shock absorbers, and transmission
- Coolant level and concentration check
- Convertible-specific: Inspection of the power top hydraulic system and operation
Serpentine Belt Inspection
Specialists recommend inspecting the serpentine belt every 30,000 miles for wear or cracks and replacing as needed .
Transmission Information
The 2012 BMW 135i Convertible is available with either a 6-speed manual or a 7-speed DCT (dual-clutch) transmission.
Manual Transmission
BMW specifies fluids conforming to MTF-LT-3 or SAF-XLS/SAF-XJ specifications with a typical viscosity of 75W-90.
Owner Guidance: The manual transmission is one of the most neglected service areas on a car. Manual transmissions should have their fluid replaced within the 40,000 to 60,000 mile range .
DCT (Dual-Clutch Transmission)
For the DCT transmission, BMW specifies Pentosin DCTF-1 fluid. BMW considers DCT fluid a lifetime fill with no specified change interval.
Owner Guidance: For automatic transmissions, BMW does not specify a change interval, but replacing the fluid every 40,000 to 60,000 miles is advised by independent specialists .
Rear Differential
The rear differential has a fluid capacity of approximately 1.2 liters. Specialist recommendations typically suggest differential fluid service every 40,000–60,000 miles for optimal longevity.
Recommended Maintenance Planning
For 2012 BMW 135i Convertible vehicles, consider the following service items based on factory and specialist recommendations:
| Component | Factory/OEM Guidance | Owner Guidance Notes |
|---|---|---|
| Engine Oil | 10,000 miles / 12 months | 5,000–7,000 miles for modified or aggressive driving; 6.5L capacity; BMW LL-01 approved synthetic |
| Spark Plugs | 60,000 miles | 30,000–40,000 miles for modified vehicles |
| Ignition Coils | As needed | Replace with spark plugs as preventive maintenance |
| Brake Fluid | 2 years | Fixed interval per BMW documentation |
| Engine Air Filter | 30,000 miles | Inspect more frequently in dusty conditions |
| Coolant | 4 years or 60,000 miles | Use BMW-approved coolant |
| Manual Transmission Fluid | As per service manual | 40,000–60,000 miles; MTF-LT-3 spec; 75W-90 |
| DCT/Automatic Transmission Fluid | Lifetime fill | 40,000–60,000 miles (specialist recommendation) |
| Serpentine Belt | Inspect 30,000 miles | Replace as needed |
| Vehicle Check | As per CBS | Comprehensive inspection including convertible top |
Frequently Asked Questions
How often should I change the oil on my 2012 BMW 135i Convertible?
BMW suggests oil changes approximately every 10,000 miles or 12 months, depending on driving habits . For owners driving aggressively or with modifications, a shorter interval of 5,000 to 7,000 miles is recommended . The N55 engine capacity is 6.5 liters .
What engine oil should I use in my 2012 BMW 135i Convertible?
BMW recommends synthetic oils meeting Longlife-01 (LL-01) specifications . Approved viscosity grades include SAE 5W-30 and 5W-40 . Motul 8100 X-cess 5W-40 is one option that meets BMW LL-01 approval .
When should I replace the spark plugs on my 2012 BMW 135i Convertible?
BMW recommends replacing spark plugs at 60,000 miles for the N55 engine . For modified vehicles or those driven aggressively, specialists recommend replacement every 30,000–40,000 miles .
How often should I change the brake fluid?
Brake fluid must be replaced every two years, per BMW's factory maintenance requirements .
Does the 2012 BMW 135i Convertible require transmission fluid service?
BMW considers automatic transmission fluid a lifetime fill with no specified interval. However, independent specialists recommend replacing the fluid every 40,000 to 60,000 miles . Manual transmissions should also have their fluid replaced within this range .
When should the coolant be changed on the 2012 BMW 135i Convertible?
BMW recommends replacing coolant every 4 years or 60,000 miles . Always use BMW-approved coolant to prevent corrosion and maintain cooling efficiency .
When should the serpentine belt be replaced?
Specialists recommend inspecting the serpentine belt every 30,000 miles for wear or cracks and replacing as needed .
What is the Condition Based Service (CBS) system?
CBS is BMW's onboard system that uses sensors and algorithms to evaluate driving conditions and calculate individual service requirements . It monitors engine oil, brake pads, brake fluid, vehicle check, and legally mandated inspections. Service data is stored in the remote control key .
What was the original warranty on the 2012 BMW 135i Convertible?
The 2012 BMW 135i Convertible came with BMW Ultimate Service, providing 48 months or 50,000 miles of free scheduled maintenance, along with 48-month unlimited-mile roadside assistance . This program has long since expired for this model year.
Are there common issues with the 2012 BMW 135i Convertible?
The N55 engine is generally considered reliable. Regular preventive maintenance is important for longevity. For modified vehicles or those with higher boost levels, consider replacing spark plugs every 30,000–40,000 miles . The serpentine belt should be inspected every 30,000 miles for wear or cracks .