2018 maintenance schedule
2018 BMW i3 (94Ah) with Range Extender Complete Service & Maintenance Schedule
The 2018 BMW i3 with Range Extender (REx) is a unique vehicle that pairs a 94Ah high-voltage battery and electric motor with a small 650cc two-cylinder...
Last updated
November 8, 2026
Reviewed for service schedule clarity.
Key Takeaways
- The 2018 BMW i3 REx combines an electric motor with a 650cc two-cylinder range extender engine that requires maintenance similar to a conventional gasoline engine, including oil and filter changes.
- A BMW maintenance document confirms that spark plugs and engine air filter are long-term rated and do not need periodic replacement for the REx engine .
- Brake fluid must be replaced every 2 years , and the vehicle should receive an inspection service at the same interval.
- Oil changes are generally recommended every 7,500 to 10,000 miles or 12 months, whichever comes first .
- A critical safety note: BMW recommends disconnecting the high-voltage battery before performing any engine oil and filter service on the REx system .
- All REx engine-specific maintenance is driven by BMW's Condition Based Service (CBS) system, which monitors usage patterns and notifies the driver when service is needed .
Understanding the 2018 BMW i3 (94Ah) with Range Extender
The 2018 BMW i3 with Range Extender (REx) is a unique vehicle that pairs a 94Ah high-voltage battery and electric motor with a small 650cc two-cylinder engine derived from the BMW C650 scooter . This engine does not drive the wheels; instead, it acts as a generator to recharge the battery, extending the vehicle's range. Although the REx engine operates under light and relatively constant loads, it still requires periodic maintenance, including oil and filter changes .
BMW's Condition Based Service (CBS) system monitors actual vehicle usage to determine when maintenance is needed, displaying service reminders through the vehicle's information center . For the 2018 model year, BMW's factory maintenance program covers the first 3 years or 36,000 miles, with a basic and powertrain warranty of 4 years or 50,000 miles .
Engine Oil and Filter Change
Factory Schedule
The REx engine requires oil changes at intervals determined by the CBS system, typically around 7,500 to 10,000 miles or 12 months . The i3's Condition Based Service system monitors driving conditions and the engine's operational hours to determine oil life.
BMW recommends 0W-20 synthetic oil for the i3 REx. The engine requires approximately 3 quarts of oil with filter . An oil change for the 2018 i3 REx typically costs between $46 and $60 .
Service Procedure Safety
BMW requires that the high-voltage battery be disconnected before replacing the engine oil and filter due to safety concerns when working near high-voltage components in the REx-equipped model . After service, the range extender must be operated in service mode to check the oil level and reset the service indicator. The manual start procedure requires the battery to be below a 75% state of charge .
Service Interval Reset
The service indicator can be reset by:
- Pressing the Start-Stop button (without pressing pedals) to switch on the ignition
- Holding the trip distance recorder reset button for approximately 10 seconds until the first service item is displayed
- Selecting the service item to be reset
- Pressing and holding the button until "Reset successful" appears
Brake Fluid
Factory Schedule
BMW requires brake fluid replacement every two years for the 2018 i3 . This interval is standard across all 2018 i3 variants.
Fluid Specification
The brake fluid must meet DOT4 specification . A brake fluid flush typically costs around $180 at a BMW dealership .
Vehicle Inspection
The vehicle check/inspection is performed at the same two-year interval as the brake fluid flush .
Range Extender Service Items: What's Not Required
Spark Plugs
Unlike conventional gasoline engines, the spark plugs in the i3 REx are long-term rated and do not need periodic replacement according to BMW official documentation . The REx engine operates under light duty and relatively constant speeds, minimizing spark plug wear.
Engine Air Filter
The engine air filter is also long-term rated and does not need periodic replacement . The BMW maintenance document confirms no prescribed interval for air filter replacement .
Coolant
Coolant/antifreeze is used in the cooling system. The system uses BMW-approved coolant with HT-12 Anti-Corrosion Agent for 2018-2021 models . Check levels periodically.
Maintenance Schedule Summary
| Service Item | Interval |
|---|---|
| Engine Oil & Filter Change | CBS-determined (approx. 7,500-10,000 miles / 12 months); 0W-20; 3 qt capacity |
| Brake Fluid Replacement | Every 2 years; DOT4 specification |
| Vehicle Inspection | Every 2 years |
| Spark Plugs | Long-term rated; no periodic replacement required |
| Engine Air Filter | Long-term rated; no periodic replacement required |
| 12V Battery Replacement | As needed (typically 3-5 years) |
Maintenance questions
2018 BMW i3 (94Ah) with Range Extender FAQs
How often does the 2018 BMW i3 REx need an oil change?+
The CBS system determines the interval based on driving conditions, generally around 7,500 to 10,000 miles or 12 months, whichever comes first .
What type of engine oil does the 2018 BMW i3 REx use?+
BMW recommends 0W-20 synthetic oil. The engine takes approximately 3 quarts with filter .
Does the i3 REx require spark plug replacement?+
No. BMW official documentation confirms the spark plugs are long-term rated and do not need periodic replacement .
When should the brake fluid be changed?+
BMW requires brake fluid replacement every two years for the 2018 i3 .
Does the i3 REx require a timing belt or chain replacement?+
The REx engine uses a timing chain, which should last well beyond the serviceable life of the vehicle given the REx's duty cycle .
What is the service interval for the engine air filter?+
The engine air filter is long-term rated and does not require periodic replacement .
Can I change the oil myself on the 2018 i3 REx?+
Yes, but BMW recommends disconnecting the high-voltage battery before performing any engine oil and filter service for safety reasons .
What is the warranty coverage for the 2018 BMW i3 REx?+
The 2018 BMW i3 includes a 4-year/50,000-mile basic warranty, a 4-year/50,000-mile powertrain warranty, a 12-year/unlimited-mile corrosion warranty, and a 3-year/36,000-mile scheduled maintenance program .
What brake fluid specification does the i3 REx require?+
The i3 REx requires DOT4 brake fluid .
How does the Condition Based Service system work?+
The CBS system monitors driving conditions and engine usage to calculate personalized maintenance intervals, displaying service reminders through the vehicle's information center .