2014 BMW i3 REX Complete Service & Maintenance Schedule

Key Takeaways

• The 2014 BMW i3 REX features a 650cc two-cylinder range extender engine that acts as a generator to recharge the battery, extending the vehicle's range to approximately 150 miles (EPA) .
• Engine oil and filter changes are determined by BMW's Condition Based Service system, with a documented oil change occurring at approximately 12,000 miles ; the engine requires approximately 2.75 liters (about 3 quarts) of 5W-30 synthetic oil .
• Brake fluid must be replaced every 2 years due to moisture absorption; the vehicle check is typically performed at the same interval .
• Spark plugs and engine air filter are officially "long-term rated" and do not need periodic replacement under normal operating conditions .
• A critical Safety Recall (17V-088) affects the 2014 i3 REX for inspection and potential replacement of the fuel tank vent line; approximately 19,130 U.S. vehicles are potentially affected .
• The REX engine uses a timing chain, not a belt; given the engine's light duty cycle, it is expected to last well beyond the vehicle's serviceable life .
• There is no prescribed coolant change interval, though some sources suggest a conservative 150,000-mile or 5-year guideline for the REX coolant circuit .

Understanding the 2014 BMW i3 REX

The 2014 BMW i3 with Range Extender (REX) is a unique plug-in hybrid vehicle that pairs a high-voltage battery and electric motor with a small 647 cc two-cylinder engine derived from the BMW C650 scooter . This engine does not drive the wheels; it functions purely as a generator to recharge the battery when the charge level drops to a pre-specified point, extending the vehicle's total range to about 150 miles under EPA testing .

Because the REX engine operates under light and relatively constant loads, its service requirements differ significantly from conventional gasoline engines. The engine is designed primarily as an emergency backup rather than for long-distance travel . In fact, by 2016, BMW noted the REX was being regularly used in fewer than 5% of i3s .

BMW's Condition Based Service (CBS) system monitors actual vehicle usage—including driving conditions and engine operating hours—to determine maintenance needs. Service reminders are displayed through the vehicle's information center .

BMW Factory Warranty and Maintenance Program

The 2014 BMW i3 REX was sold with comprehensive factory coverage:

• Basic Warranty: 4 years / 50,000 miles
• Powertrain Warranty: 4 years / 50,000 miles
• Corrosion Perforation Warranty: 12 years / Unlimited miles
• Roadside Assistance: 4 years / Unlimited miles
• Scheduled Maintenance: 3 years / 36,000 miles

Service Inclusive Plans: For the 2014 i3, BMW offered service plans covering 5 years or 60,000 miles, typically including brake fluid changes, cabin filter replacements, and vehicle checks .

Engine Oil and Filter Change

Factory Schedule

The REX engine requires oil changes at intervals determined by the CBS system. A documented 2014 i3 REX had its first oil and filter change at approximately 12,000 miles and a second at approximately 29,515 miles .

Oil Capacity and Specification:

• Capacity: Approximately 2.75 liters (about 3 quarts)
• Recommended Oil: 5W-30 synthetic oil meeting BMW specifications
• Filter: OEM Mahle oil filter

Service Procedure

• The oil filter should be changed with every oil change
• A drain plug seal ring should be replaced at each oil change
• The oil fill cap seal should be inspected; a 2014 i3 REX example required reattachment of the seal due to an oil leak at 29,680 miles

Owner Guidance

Some independent specialists recommend an annual oil change as a conservative measure, particularly given the extended periods between REX engine use . General forum consensus suggests a 12-month oil/filter change interval for the REX engine .

Brake Fluid Replacement

BMW requires brake fluid replacement every 2 years for the i3, including the REX variant . The brake fluid must meet DOT4 specification.

Owner Guidance: Brake fluid is hygroscopic, absorbing moisture from the air over time, which can cause corrosion within the braking system and degrade brake pedal feel. Some owners report switching to a 3-year schedule using extended-life fluid, but the BMW recommendation remains the safest approach.

Vehicle Check/Inspection

A comprehensive vehicle check is typically performed at the same 2-year interval as the brake fluid replacement. The CBS system will indicate when this inspection is due.

Spark Plugs: Officially Long-Term Rated

A BMW official maintenance document confirms: "Due to the light duty and relatively constant operating speeds, the range extender engine's spark plugs and air filter are long-term rated, which do not need periodic replacement" .

Owner Guidance: The REX engine uses two spark plugs (NGK LMAR8AI-8E or BMW Part No. 12122357197) . Some owners have replaced spark plugs when experiencing drivetrain errors or misfire codes, but this is not a scheduled maintenance item . Unless the CBS system indicates a need, most owners may not need to address spark plugs during the vehicle's service life.

Engine Air Filter

Similar to spark plugs, BMW's official documentation states the engine air filter is long-term rated and does not need periodic replacement under normal operating conditions .

Cooling System

Coolant Circuits

The i3 REX has multiple cooling circuits :

• REX engine cooling circuit: Black expansion tank, uses BMW-approved coolant mixed 50/50 with distilled water
• Electric motor cooling circuit: White expansion tank, uses BMW Part# 82141467704
• Battery cooling circuit: Uses BMW Part# 83512355296

Service Interval

There is no prescribed coolant change interval in BMW's official documentation . One forum discussion referenced a guideline of approximately 150,000 miles or 5 years for the REX coolant circuit, but this is not official BMW guidance .

Owner Guidance: Some owners recommend annual pH testing of the coolant using automotive test strips to prevent internal corrosion . The cooling system should be inspected for leaks; the coolant expansion tank has been identified as a potential failure point .

Important Safety Recall: 17V-088 (Fuel Tank Vent Line)

Affected Vehicles

This safety recall affects certain 2014-2017 BMW i3 REX models produced between March 2014 and December 2016 . Approximately 19,130 U.S. vehicles are potentially affected .

Issue

A section of the fuel tank vent line adjacent to the positive battery cable sleeve may wear through over time, potentially causing a fuel vapor leak in the engine compartment, which in the presence of an ignition source can increase the risk of a fire .

Correction

The repair includes:

• Inspection of the fuel tank vent line; replacement if damaged
• Installation of a clip between the vent line and the B+ cable to prevent contact and chafing

Owner Action: Owners should verify whether this recall has been completed on their vehicle. The recall began April 3, 2017, and is performed free of charge at authorized BMW centers .

Service Action: Motor Mount Screws

A Service Action (SI B22 01 15) addresses replacement of motor mount screws on i3 and i3 REX models produced from September 2013 to November 2015 . A sudden loss of traction while accelerating sharply may damage the engine mounts. The REX variant requires replacement of both left and right side mount screws . A documented 2014 i3 REX had engine mount screws replaced at approximately 29,515 miles .

REX Maintenance Cycle

The REX engine automatically performs a self-maintenance cycle if it has not been used for an extended period. During this cycle, the REX engine runs briefly to lubricate internal components and ensure proper operation. This is a normal function and does not require user intervention.

Summary Maintenance Schedule