HKS 15999-AM001 Low Temp Oil Cooler Thermostat for Mitsubishi Lancer Evo I-X

Vehicle Fitment

• 1992-1994 Mitsubishi Lancer Evolution I (CD9A, 4G63)
• 1994-1995 Mitsubishi Lancer Evolution II (CE9A, 4G63)
• 1995-1996 Mitsubishi Lancer Evolution III (CE9A, 4G63)
• 1996-1997 Mitsubishi Lancer Evolution IV (CN9A, 4G63)
• 1998 Mitsubishi Lancer Evolution V (CP9A, 4G63)
• 1999-2001 Mitsubishi Lancer Evolution VI (CP9A, 4G63)
• 2001-2003 Mitsubishi Lancer Evolution VII (CT9A, 4G63)
• 2003-2005 Mitsubishi Lancer Evolution VIII (CT9A, 4G63)
• 2005-2007 Mitsubishi Lancer Evolution IX (CT9A, 4G63)
• 2007-2015 Mitsubishi Lancer Evolution X (CZ4A, 4B11)
• This thermostat can be used with factory and HKS oil cooler kits on Evo models.

Features

• Low-temperature thermostat for oil cooler systems
• Opens at ~75 °C for earlier oil cooling engagement
• Improves oil temperature regulation under load
• Drop-in replacement for stock oil thermostat
• Works with factory and aftermarket oil cooler kits
• Helps reduce oil overheating during spirited driving or track use
• Durable construction for reliable thermal cycling
• Simple bolt-in component for maintenance or upgrade

Specifications

• Part Number: 15999-AM001
• Type: Low temperature oil cooler thermostat
• Opening Temperature: ~75 °C (versus ~100 °C stock)
• Compatibility: Mitsubishi Lancer Evolution I through X
• Function: Controls oil cooler bypass flow based on temp
• Material: Metal housing with precision thermal element
• Installation: Direct replacement for OEM oil thermostat
• Application: Improves engine oil temperature control for performance driving

Included Components

• 1x HKS Low Temperature Oil Cooler Thermostat (15999-AM001)

Product Description

The HKS 15999-AM001 Low Temp Oil Cooler Thermostat is a performance-oriented replacement thermostat designed for the Mitsubishi Lancer Evolution series from Evo I through Evo X. Unlike the stock thermostat that typically opens around 100 °C, this HKS unit opens earlier at approximately 75 °C, allowing engine oil to flow through the cooler sooner under rising temperatures. This helps maintain safer oil temperatures during spirited driving or track use, benefiting lubrication efficiency and engine reliability.

This thermostat fits directly into the existing oil system and can be used with both factory oil coolers and aftermarket oil cooling kits. By engaging oil cooling at a lower temperature threshold, the 15999-AM001 helps prevent excessive heat buildup in the engine oil, which can reduce wear and improve performance consistency under demanding conditions. Its straightforward bolt-in design makes it a practical maintenance upgrade or part replacement when refreshed cooling system components are installed.