Koyo Aluminum Radiator – 2006-2013 Lexus IS250 / IS350 | 2.5L & 3.5L | 6MT & AT

Upgrade or replace your IS250 or IS350’s cooling system with the Koyo Aluminum Radiator (KH011937) — a direct-fit, high-performance aluminum radiator engineered for the 2006–2013 Lexus IS250 and IS350 (XE20). Compatible with both the 2.5L 4GR-FSE and 3.5L 2GR-FSE engines, and both 6-speed manual and automatic transmission configurations, Koyo’s radiator delivers superior heat rejection over the factory unit — keeping coolant temperatures in check for both daily driving and performance use. Backed by Koyo’s reputation as one of Japan’s most respected OEM and aftermarket radiator manufacturers.

Key Features:

• Aluminum construction — full aluminum core and tanks for superior heat transfer versus the factory plastic-tank/aluminum-core OEM radiator
• Direct-fit replacement — engineered for direct installation in the 2006–2013 Lexus IS250/IS350 without modification
• IS250 and IS350 compatible — fits both the 2.5L 4GR-FSE and 3.5L 2GR-FSE engine variants
• 6MT and AT compatible — fits both 6-speed manual and automatic transmission configurations
• Koyo quality — engineered by one of Japan’s most respected OEM and aftermarket radiator manufacturers, supplying radiators to major Japanese automakers
• Superior heat rejection — improved cooling capacity over the factory radiator for sustained performance and reliability

Performance Benefits:

• Superior Heat Rejection: Koyo’s aluminum radiator provides greater heat rejection capacity than the factory plastic-tank radiator — maintaining lower coolant temperatures under the sustained high-load conditions of performance driving, spirited street use, and track days
• All-Aluminum Construction: Full aluminum construction eliminates the plastic end tanks of the factory radiator — plastic tanks are a common failure point that crack and leak over time, particularly in vehicles subjected to repeated heat cycling. An all-aluminum radiator is more durable and provides better thermal conductivity than the factory plastic-tank design
• Consistent Coolant Temperatures: Improved heat rejection capacity maintains more consistent coolant temperatures across a wider range of driving conditions — reducing the temperature spikes that can occur with the factory radiator during sustained high-load driving
• Long-Term Reliability: Aluminum construction resists the corrosion and degradation that affects factory radiators over time — particularly important in Canadian climates where road salt and freeze-thaw cycles accelerate radiator deterioration
• OEM Replacement Quality: Koyo’s OEM supplier heritage ensures the radiator meets or exceeds the factory specification for fitment, flow rate, and cooling capacity

Specifications:

• Brand: Koyo
• Part Number: KH011937
• Construction: All-aluminum
• Fitment: Direct replacement
• Application: 2006–2013 Lexus IS250 / IS350 (XE20)
• Engine Compatibility: 2.5L 4GR-FSE / 3.5L 2GR-FSE
• Transmission Compatibility: 6-speed manual (6MT) and automatic (AT)

Fitment Information:

• 2006–2013 Lexus IS250 (XE20) — 2.5L 4GR-FSE V6
• 2006–2013 Lexus IS350 (XE20) — 3.5L 2GR-FSE V6
• Transmission: 6-speed manual (6MT) and automatic (AT)
• Note: Verify your specific year, engine, and transmission configuration before ordering. Confirm fitment with Koyo for your exact IS250/IS350 variant.
• Installation: Professional installation recommended — coolant system work requires proper draining, flushing, and refilling procedures

What’s Included:

• Koyo aluminum radiator (KH011937)
• Installation instructions

Installation Notes:

• Professional installation recommended
• Drain and flush the cooling system before installation
• Replace the coolant with fresh OEM-specification coolant — Lexus/Toyota Super Long Life Coolant (SLLC) or equivalent
• Inspect all coolant hoses and clamps and replace if worn or cracked during installation
• Bleed the cooling system thoroughly after installation to remove air pockets
• Check for coolant leaks after the first heat cycle
• Monitor coolant temperature for the first several heat cycles to verify correct operation

Why Upgrade to a Koyo Radiator?

The factory Lexus IS250/IS350 radiator uses an aluminum core with plastic end tanks — a design that is adequate for stock driving conditions but has known long-term durability limitations. Plastic end tanks are prone to cracking and leaking over time, particularly in vehicles subjected to repeated heat cycling, high ambient temperatures, or performance driving. When the factory radiator fails, replacing it with a Koyo all-aluminum unit eliminates the plastic tank failure mode entirely and provides improved heat rejection capacity for the IS250/IS350’s V6 engine. Koyo’s direct-fit design ensures the replacement is straightforward — no modification required, with correct fitment for all hose connections, mounting points, and transmission cooler lines (AT variants).

The Lexus IS250/IS350 (XE20) Platform:

The 2006–2013 Lexus IS250 and IS350 (XE20) are rear-wheel-drive luxury sport sedans built on Toyota’s IS platform — powered by the naturally aspirated 4GR-FSE 2.5L V6 (IS250) and 2GR-FSE 3.5L V6 (IS350). The XE20 IS has become an increasingly popular platform for performance enthusiasts — particularly the IS350 with its 306hp 2GR-FSE, which responds well to bolt-on modifications and is a capable track day and performance street platform. A quality radiator upgrade is a foundational reliability improvement for any IS250/IS350 build, ensuring the cooling system can handle the demands of performance driving without the risk of factory radiator failure.

Why Koyo?

Koyo Radiator Co., Ltd. is one of Japan’s most respected radiator manufacturers — an OEM supplier to Toyota, Honda, Nissan, and other major Japanese automakers, with decades of experience in radiator engineering and manufacturing. Their aftermarket radiator lineup applies the same engineering standards as their OEM products, delivering direct-fit replacements with improved materials and construction versus the factory units. For IS250/IS350 owners who want a radiator that meets or exceeds OEM quality standards, Koyo is the definitive choice.

Perfect For:

• 2006–2013 Lexus IS250 and IS350 owners replacing a failed or leaking factory radiator
• IS350 performance builds where improved cooling capacity is needed for track day and spirited street use
• IS250/IS350 owners who want to proactively replace the factory plastic-tank radiator with a more durable all-aluminum unit
• High-mileage IS250/IS350 builds where the factory radiator is approaching end of service life
• Anyone who wants Koyo’s OEM-supplier quality and all-aluminum construction in a direct-fit IS250/IS350 radiator

Pro Tip: Replace the coolant hoses and thermostat at the same time as the radiator. If the radiator has failed or is being replaced due to age, the hoses and thermostat are likely at a similar service life stage — replacing them together eliminates the risk of a hose or thermostat failure requiring a second coolant system service shortly after the radiator replacement.

Note: Use Lexus/Toyota Super Long Life Coolant (SLLC) or an equivalent OAT coolant when refilling — do not mix coolant types. Bleed the cooling system thoroughly after installation to prevent air pockets that can cause overheating.