2008 BMW 135i Service Schedule & Maintenance Guide

Key Takeaways

• The 2008 BMW 135i is powered by the N54 3.0-liter twin-turbo inline-6 engine, producing 300 horsepower and available as a Coupe (E82) or Convertible (E88).
• 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 .
• For the N54 engine, BMW specifies spark plug replacement at 45,000 miles .
• Brake fluid requires replacement every two years as a fixed time-based interval .
• Automatic transmission fluid (ATF) replacement is specified at intervals of 100,000 miles .
• The original 4-year/50,000-mile BMW Ultimate Service free maintenance program has long since expired for this model year.

Understanding the BMW Condition Based Service System

The 2008 BMW 135i utilizes the Condition Based Service (CBS) system, a sophisticated maintenance monitoring approach that represents a departure from traditional fixed-interval schedules. Sensors and special algorithms take the different driving conditions of your BMW into account to determine current and future service requirements .

What CBS Monitors

On the Control Display or instrument cluster, you can view remaining times or distances for :

• Engine oil service
• Front brake pads
• 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 2008 BMW 135i based on BMW technical documentation.

Engine Oil Service

The CBS system determines engine oil change intervals based on driving conditions rather than a fixed mileage schedule.

Oil Specifications: The N54 engine requires BMW-approved synthetic oils. BMW recommends using engine oils that meet BMW's Longlife-01 (LL-01) specifications. BMW TwinPower Turbo 0W30 synthetic oil and OEM Mahle oil filter kits are specified for N54/N55 engines. Mahle is an OE supplier to BMW for oil filters, and their products meet or exceed BMW requirements .

Owner Guidance: The N54 twin-turbo engine places considerable thermal stress on engine oil. A disciplined maintenance approach with regular oil changes is strongly recommended by independent specialists to ensure longevity of the turbochargers and engine components.

Spark Plug Service

For the N54 engine in the 2008 135i, BMW specifies spark plug replacement at 45,000 miles .

Spark Plug Specifications:

• Bosch ZGR6STE2 plugs are specified for 2007-2010 N54 engines
• NGK Laser Iridium plugs (ILZKBR7B8DG) are available as an upgrade option for N54 applications, though these require gapping to precisely 0.022 inches (0.56mm) and have a replacement interval of approximately half the OEM Bosch plug (15,000-20,000 miles)

Owner Guidance: Replacing spark plugs ahead of the factory interval is recommended, especially if your BMW has been tuned for increased performance. Replacing ignition coils as preventive maintenance at the same time as spark plugs is also recommended to ensure proper ignition system operation .

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.

The BMW maintenance schedule for the 2008 1 Series specifies "Replace brake fluid" as a maintenance item .

Owner Guidance: Brake fluid that is dark in color or has been more than two years since the last change should be replaced . BMWs typically require DOT 4 brake fluid. If brake fluid appears brown or black, it indicates significant contamination and moisture absorption that reduces braking efficiency .

Automatic Transmission Service

BMW documentation specifies automatic transmission fluid (ATF) replacement at intervals of 100,000 miles . The ATF fluid assists in lubrication, cooling, and operation of the brake bands, torque converter, and valves .

Transmission Fluid Specifications: For 2008-2010 model years, the automatic transmission uses fluids equivalent to Shell M-1375.4 and BMW ATF-2 .

Owner Guidance: Many independent specialists recommend servicing the automatic transmission more frequently than the 100,000-mile OEM interval, as the fluid degrades over time, especially with hard use.

Manual Transmission Service

For the 2008 BMW 135i manual transmission, BMW specifies fluids conforming to MTF-LT-3 specification . A typical viscosity of 75W-90 is recommended.

Owner Guidance: The manual transmission is one of the most neglected service areas on a car . The fluid assists in lubrication and heat dissipation of the transmission, and even though it is in a closed environment, the fluid can become old and contaminated. It should be checked for level and changed as per the vehicle's service manual .

Emission Control Maintenance

The maintenance schedule includes the following emission control items :

Recommended Maintenance Planning

For 2008 BMW 135i vehicles, consider the following service items based on factory and specialist recommendations:

Frequently Asked Questions

How often should I change the oil on my 2008 BMW 135i?

The CBS system determines intervals based on driving conditions. The N54 engine is turbocharged and places added stress on engine oil. BMW TwinPower Turbo 0W30 synthetic oil with an OEM Mahle oil filter is the specified combination for N54/N55 engines .

What engine oil should I use in my 2008 BMW 135i?

BMW recommends synthetic oils meeting Longlife-01 (LL-01) specifications. BMW TwinPower Turbo 0W30 synthetic oil is specified for N54/N55 turbo engines, with an OEM Mahle oil filter that meets or exceeds BMW requirements .

When should I replace the spark plugs on my 2008 BMW 135i?

BMW specifies spark plug replacement at 45,000 miles for the N54 engine . Bosch ZGR6STE2 plugs are specified for 2007-2010 N54 engines . Replacing spark plugs ahead of the factory interval is recommended for tuned vehicles .

How often should I change the brake fluid?

Brake fluid service is specified at two-year intervals per BMW OEM documentation . If brake fluid appears brown or black, it should be replaced immediately as this indicates significant contamination .

Does the 2008 BMW 135i require transmission fluid service?

BMW documentation specifies ATF replacement at 100,000 miles . For 2008-2010 models, the automatic transmission uses fluids equivalent to Shell M-1375.4 and BMW ATF-2 . For the manual transmission (2008-2010), BMW specifies fluids conforming to MTF-LT-3 specification .

What transmission fluid does the 2008 BMW 135i manual use?

For 2008-2010 manual transmission models, BMW specifies fluids conforming to MTF-LT-3 specification . A typical viscosity of 75W-90 is recommended.

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 spark plugs are used in the 2008 BMW 135i N54 engine?

Bosch ZGR6STE2 plugs are specified for 2007-2010 N54 engines . NGK Laser Iridium plugs (ILZKBR7B8DG) are available as an upgrade, requiring gapping to 0.022 inches with a 15,000-20,000 mile replacement interval .

What was the original warranty on the 2008 BMW 135i?

The 2008 BMW 135i 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.