Vehicle Compatibility

The Mishimoto MMRAD-STI-08X fits:

Subaru WRX

• 2008 Subaru WRX
• 2009 Subaru WRX
• 2010 Subaru WRX
• 2011 Subaru WRX
• 2012 Subaru WRX
• 2013 Subaru WRX
• 2014 Subaru WRX

Subaru STI

• 2008 Subaru STI
• 2009 Subaru STI
• 2010 Subaru STI
• 2011 Subaru STI
• 2012 Subaru STI
• 2013 Subaru STI
• 2014 Subaru STI
• 2015 Subaru STI

Always verify fitment before purchasing.

What Makes the X-Line Different?

The biggest difference between the standard Mishimoto radiator and the X-Line version is cooling capacity.

The MMRAD-STI-08X utilizes:

• Three-row aluminum core
• Increased coolant volume
• Greater heat dissipation capacity
• Larger cooling surface area

This design allows the radiator to manage heat more effectively during demanding driving conditions.

For modified WRXs and STIs, additional cooling capacity can be the difference between consistent performance and heat-soaked frustration.

Key Specifications

Radiator Dimensions

• Overall Size: 28″ x 21.8″ x 2.5″
• Core Size: 13.39″ x 27.09″
• Rows: 3
• Core Thickness: 2.0″
• Inlet Diameter: 1.54″
• Outlet Diameter: 1.54″
• Tank Wall Thickness: 0.08″

These dimensions provide significantly more cooling capacity than the factory radiator while maintaining direct-fit compatibility.

Triple-Core Cooling Performance

The heart of the X-Line radiator is its large three-row core.

Benefits include:

Increased Heat Dissipation

Additional rows create more surface area for transferring heat from coolant to airflow.

Greater Coolant Capacity

More coolant volume helps stabilize temperatures during prolonged high-load operation.

Improved Track-Day Performance

Repeated hard laps can overwhelm factory cooling systems. The X-Line is designed to better withstand those conditions.

Better Protection Against Heat Soak

Turbocharged Subarus are especially vulnerable to heat buildup. The larger core helps reduce temperature spikes.

Fully Brazed Aluminum Construction

Unlike factory radiators that use plastic end tanks, the X-Line features all-aluminum construction.

Advantages include:

• Improved durability
• Better resistance to pressure cycling
• Enhanced heat transfer
• Longer service life
• Reduced risk of tank failure

For aging WRX and STI models, replacing factory plastic components before they fail is often a wise preventative measure.

Polished Aluminum End Tanks

The polished aluminum end tanks provide both functional and visual benefits.

Not only do they improve durability, but they also add a clean performance appearance under the hood.

For enthusiasts building show-quality engine bays, the X-Line radiator delivers a much more premium look than the stock unit.

Direct OEM Fitment

Despite its larger cooling capacity, the Mishimoto X-Line radiator is designed as a direct replacement.

Installation benefits include:

• Bolt-in fitment
• No cutting required
• No fabrication necessary
• Compatible with factory mounting locations

This makes installation significantly easier compared to custom cooling solutions.

Included 1.3 Bar Radiator Cap

Every X-Line radiator includes a Mishimoto 1.3-bar high-pressure radiator cap.

Benefits include:

• Higher coolant boiling point
• Improved pressure control
• Enhanced cooling system performance
• Better protection during aggressive driving

This added pressure capability helps maximize the effectiveness of the upgraded radiator.

Perfect for Modified WRXs and STIs

The MMRAD-STI-08X is especially beneficial for:

• Stage 2 WRX builds
• Big turbo STI projects
• Track-day cars
• Time attack vehicles
• Rallycross builds
• High-horsepower street cars

The more power you make, the more valuable additional cooling becomes.

Mishimoto Warranty Protection

Mishimoto backs the X-Line radiator with one of the strongest warranty programs in the aftermarket industry.

The warranty includes:

• Lifetime coverage
• Accident protection
• Product support

This provides peace of mind for owners investing in a premium cooling upgrade.

Final Verdict

The Mishimoto MMRAD-STI-08X X-Line Performance Aluminum Radiator is one of the best cooling upgrades available for the 2008-2014 Subaru WRX and 2008-2015 STI. Its triple-core design, all-aluminum construction, direct-fit installation, and track-capable cooling performance make it an excellent choice for both daily-driven and heavily modified Subarus.

If your goals include higher horsepower, improved reliability, or consistent performance under demanding conditions, the X-Line radiator is a worthwhile investment that helps protect one of the most important components in your Subaru: the engine.