Segment:
Performance Compact Sedan/Hatchback
Niche:
Rally-inspired, all-wheel-drive performance car with a strong enthusiast following.
Key Competitors:
Mitsubishi Lancer Evolution (previous generation), Ford Focus RS (later generation), Volkswagen Golf R, Audi S3.
Differentiators:
Iconic EJ257 engine, Symmetrical All-Wheel Drive system with Driver Controlled Centre Differential (DCCD), hydraulic power steering, Brembo brakes, robust chassis, legendary rally heritage.
Primary Users:
Professional automotive technicians, experienced DIY mechanics, Subaru enthusiasts seeking in-depth repair and maintenance knowledge.
Powertrain:
Engine (EJ257), turbocharged intercooled, DOHC, 16-valve Boxer; Drivetrain (Symmetrical All-Wheel Drive, DCCD, differentials); Transmission (6-speed manual); Fuel System; Exhaust System.
Chassis:
Suspension (front MacPherson struts, rear double wishbone, STI-specific tuning); Steering (power rack and pinion); Brakes (Brembo front and rear calipers, vented discs); Wheels and Tires; Frame and Body Structure.
Electrical:
Engine Control Module (ECM), Powertrain Control Module (PCM); Lighting System; Instrument Cluster; Audio System; HVAC Controls; Power Accessories; Security System; SRS (Airbag) System; CAN Bus Architecture.
Body:
Exterior Panels; Interior Trim; Doors; Windows; Seats; Roof; Bumpers; Aerodynamics.
Maintenance:
Scheduled maintenance, oil changes, filter replacements, fluid checks and top-offs, spark plug replacement, brake pad inspection.
Troubleshooting:
Diagnostic Trouble Codes (DTCs), symptom-based troubleshooting, electrical circuit diagnosis, performance issues.
Repair:
Engine component removal and installation (pistons, rods, crankshaft, valves, turbocharger); transmission overhaul; brake caliper replacement; suspension component renewal; electrical component repair and replacement.
Diagnostics:
OBD-II diagnostics, sensor testing, actuator testing, ECU diagnosis, live data analysis.
Depth:
Comprehensive diagnostic procedures, detailed exploded views, torque specifications, wiring diagrams, specific tool requirements, step-by-step repair instructions, overhaul procedures for major components.
Engine Type:
EJ257 Boxer H4
Aspiration:
Twin-Scroll Turbocharged with Intercooler
Displacement:
2.5 Liters (2457 cc)
Bore X Stroke:
99.5 mm x 80.0 mm
Horsepower:
305 HP @ 6000 RPM
Torque:
290 lb-ft (393 Nm) @ 4000 RPM
Fuel Type:
Premium Unleaded Gasoline (91 Octane or higher recommended)
Injection Type:
Multi-Point Fuel Injection (MPI) with Sequential Electronic Control
ECU Model:
Denso ECU (specific part numbers vary)
Oil Capacity Quarts:
5.5 US Quarts (5.2 Liters) with filter change
Oil Specification:
SAE 5W-30 (API SN, ILSAC GF-5 or equivalent)
Type:
6-Speed Manual Transmission
Type:
N/A (STI exclusively manual for this generation)
Dccd:
Driver Controlled Centre Differential (DCCD) for adjustable torque split.
Transmission Oil:
2.3 US Quarts (2.2 Liters)
Transmission Oil Type:
Subaru ExtraS II or equivalent (75W-90 GL-5 manual transmission fluid)
Fluid Capacity Quarts:
0.5 US Quarts (0.5 Liters)
Fluid Type:
75W-90 GL-5 gear oil
Fluid Capacity Quarts:
0.6 US Quarts (0.6 Liters)
Fluid Type:
75W-90 GL-5 gear oil
NHTSA Overall Rating:
4 Stars (2015 Model Year)
IIHS Top Safety Pick:
Good (for 2015 model year variants tested)
ABS:
Anti-lock Braking System (ABS) with Electronic Brake-force Distribution (EBD)
Traction Control:
Vehicle Stability Control (VSC) and Traction Control System (TCS).
AWD:
Symmetrical All-Wheel Drive system with DCCD.
Airbags:
Driver and front passenger airbags, front side-impact airbags, side curtain airbags.
Seatbelts:
3-point height-adjustable front seatbelts with pretensioners and load limiters, rear 3-point seatbelts.
Child Anchors:
LATCH (Lower Anchors and Tethers for Children) system.
Display Size:
6.1-inch touchscreen (standard) or 7-inch touchscreen (optional on Limited trims).
Audio System:
Subaru Starlink infotainment system, CD player, MP3 playback, AM/FM/SiriusXM satellite radio, Bluetooth audio streaming and hands-free calling.
Navigation:
Optional GPS navigation system.
Rearview Camera:
Standard on all trims.
Eyesight System:
Not available on WRX STI models for 2015 (standard on other Impreza trims).
Usb Ports:
Yes (typically one or two).
Oil Change Interval:
Every 6,000 miles or 6 months, whichever comes first (severe driving conditions may require more frequent changes).
Engine Air Filter:
Inspect every 15,000 miles, replace as needed.
Cabin Air Filter:
Inspect every 15,000 miles, replace as needed.
Spark Plugs:
Replace every 60,000 miles (Iridium type).
Brake Fluid:
Replace every 30,000 miles or 36 months.
Transmission Fluid:
Replace every 30,000 miles or 36 months (manual transmission, front and rear differentials).
Coolant:
Subaru Super Coolant (Blue) or equivalent, 50/50 mix with distilled water.
Brake Fluid Type:
DOT 3 or DOT 4 (low viscosity, high temperature).
Engine Ringlands:
Potential for ringland failure in EJ257 engine under extreme stress/improper tuning. Manual covers diagnosis and repair procedures.
Clutch Wear:
Performance driving can lead to accelerated clutch wear. Manual details clutch inspection and replacement.
Hatch Rattles:
Common in hatchback models, often related to interior trim or hatch seals. Manual addresses body panel adjustments and seal maintenance.
Turbo Lag:
Characteristic of the EJ257, but manual provides diagnostic steps for abnormal turbo behavior or performance degradation.
Rally Legacy:
Subaru's long and successful history in the World Rally Championship (WRC) with multiple driver and manufacturer titles, directly influencing the WRX STI's development.
Generation:
This model is part of the fourth generation Subaru Impreza (GJ/GP/GV/GR), with the WRX STI being the performance variant.
Performance Focus:
The WRX STI line has always prioritized performance, handling, and driver engagement, differentiating it from the standard Impreza models.
Manufacturing Location:
Ota City, Gunma Prefecture, Japan.
Specific Model Year:
2015
Motor Trend Award:
Subaru WRX and WRX STI were often contenders for performance car awards in their respective years, though specific wins vary.
Consumer Reports Ratings:
Subject to ongoing reviews, typically rated well for performance but sometimes lower for predicted reliability compared to mainstream vehicles.
Enthusiast Following:
Consistently ranks high among automotive enthusiasts for its driving dynamics and performance capabilities.