2011 BMW 135i Convertible Maintenance Schedule & Service Intervals

Key Takeaways

• The 2011 BMW 135i Convertible is powered by the N55 3.0-liter single-twin-scroll turbocharged inline-6 engine, producing 300 horsepower and 300 lb-ft of torque . This marks a significant change from the 2010 model year, which used the twin-turbo N54 engine .
• BMW employs a Condition Based Service (CBS) system that uses sensors and algorithms to calculate individualized service intervals based on actual driving conditions rather than fixed mileage for every item .
• The original 4-year/50,000-mile BMW Ultimate Service free maintenance program has long since expired for this model year .
• 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 .
• For the 2011 model year, the 135i Convertible can be equipped with either a 6-speed manual transmission or a new 7-speed Double Clutch Transmission (DCT), which replaces the previous Steptronic automatic option .

Understanding the BMW Condition Based Service (CBS) System

The 2011 BMW 135i Convertible utilizes 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 take the different driving conditions of your BMW into account 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 2011 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's generic service interval is listed as 15,000 miles between each service . The N55 engine has an oil capacity of approximately 6.5 liters .

Oil Specifications: The N55 engine requires BMW-approved synthetic oils. The OEM specification is BMW Longlife-01 (LL-01) . Recommended viscosity grades include 0W-30, 5W-30, and 5W-40 fully synthetic Longlife oils . BMW TwinPower Turbo 0W30 synthetic oil is the recommended oil, used with an OEM Mann oil filter kit .

Owner Guidance: For N55 engines that are tuned, used on track, or have exceeded 80,000 miles, specialists recommend increasing servicing intervals to 5,000 miles to prevent engine damage . For standard use, a 7,500 to 10,000-mile interval is recommended for preventative maintenance .

Spark Plug Service

For the N55 engine in the 2011 135i, BMW recommends replacing spark plugs at 60,000 miles.

Owner Guidance: For modified vehicles or those with higher boost levels, specialists recommend replacing spark plugs more frequently—approximately every 30,000–40,000 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.

Air Filter Replacement

The engine air filter should be inspected and replaced at suggested service intervals as part of routine maintenance. Maintaining the air filter at suggested service intervals will result in better performance and improved fuel economy.

Coolant Service

Specialists recommend replacing the coolant every 4 years or 60,000 miles as a conservative preventive measure. 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

Break-in Period

For the 2011 135i Convertible, BMW specifies a break-in period for the engine and differential. Up to 1,200 miles (2,000 km), drive at varying engine and road speeds, but do not exceed an engine speed of 4,500 rpm or a road speed of 100 mph (160 km/h). Avoid full-throttle operation and use of the transmission's kickdown mode .

Transmission Information

The 2011 BMW 135i Convertible is available with either a 6-speed manual transmission or a 7-speed Double Clutch Transmission (DCT), which replaces the previous Steptronic automatic option for the 135i .

6-Speed Manual Transmission

BMW specifies fluids conforming to MTF-LT-3 or SAF-XLS/SAF-XJ specifications with a typical viscosity of 75W-90.

7-Speed DCT (Double 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: Both manual and DCT transmissions should have their fluid replaced at regular intervals for optimal longevity. The manual transmission is one of the most neglected service areas on a car. DCT fluid service is particularly important for maintaining smooth clutch operation and preventing premature wear.

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.

Common Long-Term Ownership Considerations

Carbon Buildup (N55 Engine)

The N55 engine, like other direct-injection BMW engines, is prone to carbon buildup on the intake valves . A catch can system can help reduce carbon build-up, which is a common issue with direct fuel injection N55 engines . Symptoms of excessive carbon buildup include rough idle, reduced power, and decreased fuel economy.

Valve Cover Gasket

The original N55 valve cover is a plastic composite and is known to crack or deform over time . Oil leaks may not be coming from the gaskets and may be due to a failure of the valve cover itself . Complete valve covers with gaskets and hardware are available and may be a better choice .

Oil Consumption

The N55 engine burns oil faster than your average BMW, and therefore you will require a top-up of engine oil between services .

Recommended Maintenance Planning

For 2011 BMW 135i Convertible vehicles, consider the following service items based on factory and specialist recommendations:

Frequently Asked Questions

How often should I change the oil on my 2011 BMW 135i Convertible?

BMW lists a generic service interval of 15,000 miles . For tuned N55 engines, track use, or vehicles over 80,000 miles, specialists recommend servicing at 5,000 miles . For standard use, a 7,500–10,000-mile interval is recommended . The N55 engine capacity is 6.5 liters and requires BMW LL-01 approved synthetic oil .

What engine oil should I use in my 2011 BMW 135i Convertible?

BMW requires synthetic oils meeting Longlife-01 (LL-01) specifications . Recommended viscosity grades include 0W-30, 5W-30, and 5W-40 fully synthetic Longlife oils . BMW TwinPower Turbo 0W30 synthetic oil is recommended with an OEM Mann oil filter . For tuned or high-mileage engines, 5W-40 is recommended for better protection .

When should I replace the spark plugs on my 2011 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. Replacing ignition coils as preventive maintenance with spark plugs is also recommended.

How often should I change the brake fluid?

Brake fluid must be replaced every two years, per BMW's factory maintenance requirements .

Does the 2011 BMW 135i Convertible require transmission fluid service?

BMW considers DCT fluid a lifetime fill with no specified interval. For the manual transmission, BMW specifies MTF-LT-3 or SAF-XLS/SAF-XJ fluids. Many specialists recommend regular service for both transmission types for optimal longevity.

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 engine does the 2011 BMW 135i Convertible use?

The 2011 BMW 135i Convertible features BMW's newest 3.0-liter inline-6 engine with a single twin-scroll turbocharger and Valvetronic throttle-less intake technology, producing 300 horsepower and 300 lb-ft of torque . This is the N55 engine, which replaced the twin-turbo N54 engine used in previous model years .

What transmissions are available for the 2011 BMW 135i Convertible?

The 2011 135i Convertible is available with a standard 6-speed manual transmission or an optional 7-speed Double Clutch Transmission (DCT), which replaces the Steptronic automatic option .

What was the original warranty on the 2011 BMW 135i Convertible?

The 2011 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.

Is the N55 engine prone to carbon buildup?

Yes, the N55 engine, like other direct-injection BMW engines, is prone to carbon buildup on the intake valves . A catch can system can help reduce carbon build-up . Symptoms include rough idle, reduced power, and decreased fuel economy.