The Subaru Impreza III Sedan WRX STI 2.5, produced between 2008 and 2011, represents the pinnacle of Subaru’s rally-bred performance sedan during that generation. Positioned as the flagship trim of the Impreza III Sedan (G30 chassis), the STI 2.5 offered a significant performance upgrade over the standard Impreza and even the non-STI WRX models. It was primarily marketed towards driving enthusiasts seeking a capable all-weather performance car with a strong motorsport heritage. This model continued Subaru’s tradition of utilizing a symmetrical all-wheel-drive system and a horizontally-opposed “boxer” engine, features that became synonymous with the brand.
Technical Specifications
| Brand | Subaru |
| Model | Impreza |
| Generation | Impreza III Sedan |
| Type (Engine) | WRX STI 2.5 (293 Hp) AWD |
| Start of production | 2008 |
| End of production | 2011 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Sedan |
| Seats | 5 |
| Doors | 4 |
| Fuel consumption (urban) | 14.3 l/100 km (16.4 US mpg, 19.8 UK mpg, 7 km/l) |
| Fuel consumption (extra urban) | 8.2 l/100 km (28.7 US mpg, 34.4 UK mpg, 12.2 km/l) |
| Fuel consumption (combined) | 10.4 l/100 km (22.6 US mpg, 27.2 UK mpg, 9.6 km/l) |
| Fuel Type | Petrol (Gasoline) |
| Emission standard | Euro 4 |
| Power | 293 Hp @ 6000 rpm |
| Power per litre | 119.3 Hp/l |
| Torque | 393 Nm @ 4400 rpm (289.86 lb.-ft. @ 4400 rpm) |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | EJ257 |
| Engine displacement | 2457 cm3 (149.94 cu. in.) |
| Number of cylinders | 4 |
| Engine configuration | Boxer |
| Cylinder Bore | 99.5 mm (3.92 in.) |
| Piston Stroke | 79 mm (3.11 in.) |
| Number of valves per cylinder | 4 |
| Fuel injection system | Multi-port manifold injection |
| Engine aspiration | Turbocharger, Intercooler |
| Valvetrain | DOHC |
| Engine oil capacity | 4.3 l (4.54 US qt | 3.78 UK qt) |
| Coolant capacity | 7.7 l (8.14 US qt | 6.78 UK qt) |
| Trunk (boot) space (maximum) | 538 l (19 cu. ft.) |
| Fuel tank capacity | 60 l (15.85 US gal | 13.2 UK gal) |
| Length | 4580 mm (180.31 in.) |
| Width | 1740 mm (68.5 in.) |
| Height | 1475 mm (58.07 in.) |
| Wheelbase | 2620 mm (103.15 in.) |
| Front track | 1495 mm (58.86 in.) |
| Rear track | 1500 mm (59.06 in.) |
| Minimum turning circle | 10.6 m (34.78 ft.) |
| Drive wheel | All wheel drive (4×4) |
| Number of gears and type of gearbox | 6 gears, manual transmission |
| Front suspension | Independent type McPherson |
| Rear suspension | Several levers and rods |
| Front brakes | Ventilated discs |
| Rear brakes | Disc |
| Assisting systems | ABS (Anti-lock braking system) |
| Steering type | Steering rack and pinion |
| Tires size | 225/45 R17 |
| Wheel rims size | 17 |
Powertrain & Engine Architecture
The heart of the Impreza WRX STI 2.5 is the EJ257 2.5-liter turbocharged boxer-4 engine. This engine represented a significant upgrade from the 2.0-liter EJ207 found in earlier STI models and some international market WRX STIs. The EJ257 featured a closed-deck engine block for increased strength, a larger turbocharger, and revised internals to handle the increased power output. Fuel delivery was managed by a multi-port fuel injection system. The engine utilized a dual overhead camshaft (DOHC) valvetrain with four valves per cylinder, optimizing airflow for improved performance. The turbocharger, coupled with an intercooler, provided significant boost, contributing to the engine’s 293 horsepower and 393 Nm (289.86 lb-ft) of torque. The sole transmission option was a robust 6-speed manual gearbox, designed to withstand the engine’s power and provide precise gear changes.
Driving Characteristics
The driving experience of the Impreza STI 2.5 was distinctly focused on performance. The combination of the powerful engine, all-wheel-drive system, and manual transmission resulted in rapid acceleration and exceptional handling. The symmetrical all-wheel-drive system, a Subaru hallmark, provided excellent traction in a variety of conditions. Compared to the standard Impreza or the WRX, the STI offered a much firmer suspension setup, reducing body roll and enhancing cornering ability. However, this also resulted in a less comfortable ride on rough roads. The 6-speed manual transmission featured closely spaced gear ratios, keeping the engine within its power band for optimal acceleration. While the STI was undeniably quick, its turbocharger did exhibit some lag at lower RPMs, requiring drivers to maintain higher engine speeds for immediate response.
Equipment & Trim Levels
The WRX STI 2.5 was the highest trim level available for the Impreza Sedan. Standard features included sport seats with bolstering, a leather-wrapped steering wheel, and a comprehensive suite of performance gauges, including boost pressure and oil temperature. The interior typically featured a combination of cloth and simulated suede upholstery. Optional extras included a premium audio system, sunroof, and upgraded alloy wheels. The STI also featured unique exterior styling cues, such as a prominent rear wing, aggressive front bumper, and distinctive alloy wheel designs, differentiating it from lower trim levels.
Chassis & Braking
The Impreza STI 2.5 featured a reinforced chassis and a sophisticated suspension system designed to handle the increased power and performance. The front suspension utilized McPherson struts, while the rear employed a multi-link setup. Stabilizer bars were fitted to both the front and rear axles to reduce body roll. Braking duties were handled by ventilated disc brakes on all four wheels, providing ample stopping power. An Anti-lock Braking System (ABS) was standard, enhancing safety and control. The STI’s suspension was noticeably stiffer than that of the standard Impreza, prioritizing handling over ride comfort.
Market Reception & Comparison
The Impreza WRX STI 2.5 was generally well-received by automotive critics, who praised its performance, handling, and all-weather capability. However, some reviewers noted the firm ride quality and the presence of turbo lag. Compared to the standard Impreza and the WRX, the STI was significantly more expensive. Within the STI lineup, the 2.5-liter engine was often seen as a more refined and tractable alternative to the earlier 2.0-liter EJ207 engine, offering a broader powerband and improved low-end torque. Fuel economy, as expected for a high-performance vehicle, was relatively poor, averaging around 22.6 US mpg combined.
Legacy
The Subaru Impreza WRX STI 2.5 remains a popular choice among enthusiasts today. The EJ257 engine, while known for its potential, requires diligent maintenance, particularly regarding oil changes and cooling system upkeep. The engine is susceptible to head gasket failures if not properly maintained. Despite these potential issues, the STI 2.5 is valued for its performance, rally-bred heritage, and all-weather capability. Well-maintained examples command a premium in the used car market, and the model continues to be a popular platform for modification and performance upgrades. It represents a significant chapter in Subaru’s history, solidifying the brand’s reputation for building capable and engaging performance cars.
