2018 BMW M240i Convertible Service Requirements & Maintenance Schedule

Key Takeaways

• The 2018 BMW M240i Convertible (F23) is powered by the B58 3.0L turbocharged inline-six engine and uses BMW's Condition Based Service (CBS) system, which calculates maintenance needs based on actual driving conditions rather than fixed mileage alone
• Original factory warranty coverage included a 4-year/50,000-mile basic and powertrain warranty, along with 3 years or 36,000 miles of complimentary scheduled maintenance (BMW Ultimate Care)
• The B58 engine has an oil capacity of 6.5 liters and requires BMW Longlife-01 FE or Longlife-04 approved synthetic oil
• While the CBS system typically indicates oil changes around 10,000 miles, many independent specialists recommend a more conservative 5,000-7,500-mile interval for the turbocharged B58 engine
• Spark plugs are recommended for replacement at 30,000–60,000 miles depending on driving conditions, with some sources suggesting 30,000 miles for optimal performance

Understanding the BMW Condition Based Service System

The 2018 BMW M240i Convertible features the Condition Based Service (CBS) system, which represents a significant evolution from traditional fixed-interval maintenance. The system uses sensors and special algorithms that take into account the driving conditions of the vehicle to calculate the need for maintenance . This makes it possible to adapt the amount of maintenance corresponding to your user profile .

The CBS system monitors factors such as driving style, fuel consumption, and trip length to determine when service is actually needed. This results in variations from the base 10,000-mile interval, meaning two identical vehicles may require service at different odometer readings depending on how they have been driven . Because the system adapts to your specific driving profile, the reference intervals provided below should be used for planning purposes, but the CBS system remains the primary guide for your vehicle.

Factory Maintenance Schedule

Original Warranty and Maintenance Coverage

The 2018 BMW M240i Convertible originally came with comprehensive factory coverage :

1,200-Mile Running-In Service

The 2018 M240i Convertible requires a running-in service at approximately 1,200 miles. This service is critical for the long-term health of the vehicle and includes:

• Engine oil and filter replacement
• Rear axle differential fluid replacement
• Intercooler inspection

During the break-in period, it is recommended to vary engine speeds and avoid full throttle or kickdown. The engine should not be operated at excessively high engine speeds for extended periods.

Engine and Drivetrain Specifications

The 2018 M240i Convertible is powered by the B58 3.0L turbocharged inline-six engine.

Engine Oil Specifications

The vehicle requires DOT 4 brake fluid meeting BMW specifications .

Service Interval Summary

Oil Change Guidance

Factory Schedule: The CBS system is the primary indicator for oil change intervals, with service typically indicated around 10,000 miles or 12 months depending on driving conditions.

Owner Guidance: Many independent specialists recommend changing synthetic motor oil every 5,000 to 7,500 miles for optimal engine protection , particularly for the turbocharged B58 engine. Always replace the oil filter when changing the oil.

You may need an oil change sooner than recommended if you notice the check engine or oil change light is illuminated, hear knocking sounds from the engine, smell oil inside the vehicle, or observe excess vehicle exhaust.

Spark Plug Service

Spark plugs are recommended for replacement at approximately 30,000 miles for the B58 engine according to some specialist guidance . General BMW maintenance references indicate replacement at 60,000 miles as a standard interval. The CBS system will indicate when spark plug replacement is due based on driving conditions.

Brake Fluid Service

Brake fluid replacement is a time-based service. BMW generally recommends brake fluid replacement every 2 years to maintain optimal braking performance and prevent corrosion in the hydraulic system . The vehicle requires DOT 4 brake fluid that meets BMW specifications .

Engine Air Filter

The engine air filter should be inspected and replaced as needed, typically at intervals determined by the CBS system. General guidance suggests replacement around 30,000 miles as part of routine maintenance . In dusty operating conditions, more frequent inspection and replacement may be warranted.

Cabin Air Filter

The cabin air filter should be replaced at regular intervals to maintain air quality inside the vehicle. General guidance suggests replacement around 15,000 to 20,000 miles . The CBS system will indicate when replacement is due.

Transmission Fluid Service

Factory Schedule: BMW does not specify a fixed replacement interval for automatic transmission fluid under normal operating conditions; the fluid is often designated as a "lifetime" fill.

Owner Guidance: The transmission is one of the most neglected service areas on a vehicle. Automatic transmission fluid assists in more than just lubrication—it also supports the operation of brake bands, torque converter, and valves. Independent specialists recommend a fluid and filter service at approximately 60,000 miles as a preventive measure .

Differential Fluid Service

For the M240i, the rear axle fluid is replaced at the 1,200-mile running-in service. For longer-term maintenance, differential fluid should be checked and replaced according to the service interval—this is particularly important for vehicles frequently driven in high-performance settings. General guidance suggests differential fluid service at approximately 60,000 miles .

Cooling System Service

The cooling system should be flushed and the coolant replaced at regular intervals. General guidance suggests coolant service at approximately 60,000 miles . Using Genuine BMW Coolant/Antifreeze is recommended to maintain cooling system performance.

Maintenance Schedule Summary Table

Long-Term Ownership Considerations

Service Documentation

Maintaining complete service records is essential for warranty compliance and resale value. BMW service centers can read CBS system data stored in the vehicle to verify maintenance history. A full service history supports the vehicle's mechanical condition and reliability.

BMW Ultimate Care

The 2018 BMW M240i Convertible was originally covered under BMW Ultimate Care, which provided factory-scheduled maintenance for 3 years or 36,000 miles from the vehicle's in-service date . After this coverage expires, owners are responsible for all maintenance costs.

Battery Health

Modern BMWs rely on the battery for proper CBS system function. If the vehicle battery has been disconnected, the CBS system may not track time-based intervals accurately. A BMW service center should update the time-dependent maintenance procedures following any battery disconnection.

Cooling System

The B58 engine requires proper cooling system maintenance. Using Genuine BMW Coolant/Antifreeze is recommended to maintain cooling system performance. The coolant should be flushed and replaced according to the CBS system or at preventive intervals to prevent overheating and corrosion.

Frequently Asked Questions

What engine is in the 2018 BMW M240i Convertible?

The 2018 BMW M240i Convertible is powered by the B58 3.0L turbocharged inline-six engine, producing 335 horsepower.

How does the Condition Based Service system work?

The CBS system uses sensors and algorithms to monitor driving conditions, driving style, and fuel consumption to calculate service needs dynamically. It displays service requirements on the vehicle's display and adapts maintenance to your specific driving profile .

What is the 1,200-mile service for the M240i?

The 1,200-mile running-in service is a mandatory service that includes engine oil and filter replacement, rear axle differential fluid replacement, and intercooler inspection. This service is critical for the long-term health of the vehicle.

What type of oil does the 2018 BMW M240i Convertible require?

The B58 engine requires BMW-approved synthetic oil meeting Longlife-01 FE or Longlife-04 specifications, with SAE 5W-30 as a recommended viscosity. The engine capacity is 6.5 liters .

How often should the oil be changed?

The CBS system determines oil change intervals based on driving conditions, typically around 10,000 miles or 12 months. Many independent specialists recommend changing synthetic oil every 5,000 to 7,500 miles for optimal engine protection .

When should spark plugs be replaced?

Spark plugs are recommended for replacement at approximately 30,000–60,000 miles depending on driving conditions . The CBS system will indicate the specific timing for your vehicle.

How often should brake fluid be changed?

BMW generally recommends brake fluid replacement every 2 years to maintain braking performance and prevent corrosion . The vehicle requires DOT 4 brake fluid meeting BMW specifications .

How often should the coolant be replaced?

The cooling system should be flushed and the coolant replaced as indicated by the CBS system. Preventive guidance suggests replacement at approximately 60,000 miles .

When should the transmission fluid be changed?

BMW does not require automatic transmission fluid changes under normal conditions. For long-term reliability, many specialists recommend a fluid and filter service at approximately 60,000 miles as a preventive measure .

What was the original warranty coverage on the 2018 M240i Convertible?

The 2018 BMW M240i Convertible came with a 4-year/50,000-mile basic and powertrain warranty, 12-year/unlimited-mile corrosion perforation warranty, 4-year/unlimited-mile roadside assistance, and 3-year/36,000-mile complimentary scheduled maintenance .