2018 maintenance schedule
2018 BMW 340i xDrive Service Schedule & Maintenance Guide
The 2018 BMW 340i xDrive is the all-wheel-drive variant of the F30-generation 3 Series, powered by the highly regarded B58 3.0-liter turbocharged...
Last updated
November 4, 2026
Reviewed for service schedule clarity.
Key Takeaways
- Engine & Drivetrain: The 2018 340i xDrive is powered by the B58 3.0-liter turbocharged inline-six engine, rated at 320 horsepower and 330 lb-ft of torque, paired with BMW's xDrive all-wheel-drive system .
- Oil Change Interval: BMW's Condition Based Service (CBS) system determines the interval based on driving conditions. Independent specialists recommend a conservative 5,000 to 8,000-mile interval for optimal engine health.
- Oil Specification: The B58 engine requires BMW Longlife-approved full synthetic oil, such as LL-01, LL-14 FE+, or LL-17 FE+. The engine holds approximately 6.5 liters (6.9 quarts) with filter.
- Brake Fluid: BMW recommends replacing brake fluid every 30,000 miles (or 24 months) .
- Spark Plugs: OEM documentation specifies spark plug replacement at 100,000 miles. For modified or tuned vehicles, a shorter interval is strongly advised .
- Differential Fluid: A general recommendation for xDrive models is to change the differential fluid every 30,000 to 50,000 miles .
Understanding the 2018 BMW 340i xDrive
The 2018 BMW 340i xDrive is the all-wheel-drive variant of the F30-generation 3 Series, powered by the highly regarded B58 3.0-liter turbocharged inline-six engine . This engine is a significant evolution from its predecessor, the N55, featuring an air-to-water intercooler and a closed-deck design for enhanced strength and cooling.
The xDrive system adds a transfer case and front differential to the drivetrain, which require periodic fluid service in addition to the rear differential. The vehicle's Condition Based Service (CBS) system monitors driving conditions to determine service intervals. Service interval warnings are standard equipment .
Factory Maintenance Schedule
Based on OEM documentation for the 2018 BMW 340i, the following service intervals are specified.
| Distance | Action | Item |
|---|---|---|
| 30,000 miles | Flush/replace | Brake fluid |
| 36,000 miles | Replace | Engine air filter |
| 60,000 miles | Flush/replace | Brake fluid |
| 72,000 miles | Replace | Engine air filter |
| 90,000 miles | Flush/replace | Brake fluid |
| 100,000 miles | Replace | Spark plugs |
| 100,000 miles | Change | Automatic transmission fluid |
| 108,000 miles | Replace | Engine air filter |
| 120,000 miles | Flush/replace | Brake fluid |
| 120,000 miles | Replace | Oxygen sensor |
| 144,000 miles | Replace | Engine air filter |
| 150,000 miles | Flush/replace | Brake fluid |
Engine Oil & Filter Service
BMW Factory Schedule
BMW's Condition Based Service (CBS) system monitors your driving style, trip length, and engine load to determine the optimal oil change interval. While the CBS system can allow intervals up to 10,000 miles, many specialists recommend a more proactive approach.
Oil Specifications & Capacity
The B58 engine requires high-quality synthetic oil. The correct oil viscosity and specification are listed in your owner's manual.
Oil Capacity: The B58 engine holds approximately 6.5 liters (6.9 quarts) of oil with a filter.
Approval: BMW LL-01, LL-14 FE+, or LL-17 FE+.
Viscosity: BMW often recommends 0W-20 for fuel efficiency. 5W-30 is also a suitable option.
Owner Guidance
Motor oil is the single most important element in keeping your engine healthy. A consensus among B58 experts is to change the oil and filter every 5,000 to 8,000 miles, or at least once a year, especially for vehicles driven aggressively or tuned for higher performance.
Estimated Cost: An oil change for a 2018 BMW 340i xDrive is estimated at approximately $190–$286, with parts costing around $85 and labor at $105–$110 .
Brake Fluid Service
BMW Factory Schedule
A brake system flush and fluid replacement is a critical time-based service. The OEM schedule specifies replacing the brake fluid every 30,000 miles (or 24 months) .
Why This Service Matters
Brake fluid is hygroscopic, meaning it absorbs moisture from the air over time. Contaminated brake fluid appears dark or black and can lead to a spongy pedal feel, reduced boiling point (brake fade), and internal corrosion of brake system components. A brake system flush removes the contaminated fluid and replaces it with fresh, clean fluid.
Signs Brake Service Is Needed:
- Brake fluid appears dark, brown, or black
- Brake pedal feels spongy
- Diminished brake system performance
Spark Plug Service
BMW Factory Schedule
BMW specifies spark plug replacement at 100,000 miles .
Owner Guidance
Spark plugs are a critical wear item on the B58 engine. The high cylinder pressures and temperatures of the turbocharged engine place significant stress on the ignition system. For modified vehicles or those driven hard, many specialists recommend replacing spark plugs at a much shorter interval, sometimes as frequently as every 15,000 to 20,000 miles, to prevent misfires and maintain peak performance. Ignition coils are also considered a standard wear item and are often replaced every second time you change the spark plugs.
Estimated Cost: Spark plug replacement for the 2018 BMW 340i xDrive is estimated at approximately $610 to $936 depending on the service provider .
Differential & xDrive Drivetrain Service
The xDrive all-wheel-drive system in your 2018 BMW 340i xDrive adds front and rear differentials that require periodic fluid service in addition to the rear differential. While BMW may designate these as "lifetime fill" in some cases, independent specialists strongly recommend proactive fluid changes to ensure optimal AWD performance and longevity.
Recommended Interval: A general recommendation for all vehicles is to change the differential fluid every 30,000 to 50,000 miles .
Estimated Cost: Differential fluid service for the 2018 BMW 340i xDrive is estimated at approximately $207 for the rear and $207 for the front .
General Service Recommendations Summary
The CBS system is the ultimate authority for your specific vehicle. The following table summarizes key service intervals based on OEM documentation and specialist guidance.
| Service Item | OEM/General Guidance | Owner Guidance |
|---|---|---|
| Engine Oil & Filter | CBS-driven | Every 5,000–8,000 miles |
| Brake Fluid | 30,000 miles or 24 months | Follow manufacturer schedule |
| Spark Plugs | 100,000 miles | 15,000–20,000 miles (modified vehicles) |
| Engine Air Filter | 36,000 miles | As indicated by CBS |
| Differential Fluid | As needed | Every 30,000–50,000 miles |
| Power Steering Fluid | As needed | Consider service every 3–4 years |
Frequently Asked Questions
1. How often should I change the oil in my 2018 BMW 340i xDrive?
BMW's Condition Based Service (CBS) system may allow intervals up to 10,000 miles. However, independent specialists strongly advise a more conservative 5,000 to 8,000-mile interval for optimal engine health .
2. How much oil does the B58 engine take?
The B58 engine holds approximately 6.5 liters (6.9 quarts) of engine oil with a filter.
3. What type of oil does a 2018 BMW 340i xDrive require?
The B58 engine requires a high-quality full synthetic oil that meets BMW Longlife approvals, such as LL-01, LL-14 FE+, or LL-17 FE+. While 0W-20 is often recommended for fuel efficiency, 5W-30 is a popular alternative for better protection.
4. When should the spark plugs be changed on a B58 engine?
BMW recommends replacing spark plugs at 100,000 miles. For a modified or tuned vehicle, a shorter interval of 15,000 to 20,000 miles is strongly advised to prevent misfires .
5. How often should the brake fluid be replaced?
BMW recommends replacing the brake fluid every 30,000 miles (or 24 months) as a critical time-based service .
6. When should the transmission fluid be changed on a 2018 BMW 340i xDrive?
BMW's OEM schedule specifies an automatic transmission fluid change at 100,000 miles as a preventative measure. The ZF 8-speed transmission is a robust unit, and fluid changes at recommended intervals help ensure its longevity.
7. Does the 2018 BMW 340i xDrive require additional drivetrain maintenance?
Yes, the xDrive system adds a transfer case and front differential that require periodic fluid service. A general recommendation is to change the differential fluid every 30,000 to 50,000 miles .
8. Is the 2018 BMW 340i xDrive expensive to maintain?
Maintenance costs are above average for non-luxury vehicles but typical for a premium German performance car. Regular preventive maintenance is the key to avoiding more significant and costly repairs down the line.
*Always consult your vehicle's owner's manual and CBS system for the most accurate maintenance requirements for your specific 2018 BMW 340i xDrive. Maintenance needs may vary by production date and driving conditions.*