Upgrade the cooling system of your 2012-2015 Honda Civic Si with this Mishimoto Performance Aluminum Radiator, built to manage the sustained thermal output of a high-revving K-series engine on the street and the track. All-aluminum construction with precision TIG-welded end tanks outlasts the factory plastic-tanked unit prone to cracking under heat cycling and repeated high-rpm use. A 63% increase in core volume over the OEM radiator delivers greater surface area and thermal capacity, keeping coolant temperatures stable during back-to-back pulls, spirited street sessions, and weekend track days where the stock radiator starts to fall behind. ---- Designed as a direct-fit replacement for the 2012-2015 Honda Civic Si, this radiator drops in without cutting, fabricating, or modifications, and works seamlessly with all stock hoses and components without alteration. The included high-pressure radiator cap maintains optimal system pressure from the first drive, extracting the full benefit of the upgraded core. The Mishimoto Magnetic Drain Plug catches ferrous metallic debris before it circulates through the cooling system, protecting your K-series engine internals and extending service life beyond what the factory setup allows. ---- Don't wait for your stock radiator to crack and leave you sidelined. Whether you daily drive your Civic Si, push it hard on weekend canyon runs, or are building toward a higher-output K-series setup, this aluminum radiator handles the sustained thermal demands your factory unit was never built for. Proactive cooling upgrades protect your engine investment - and this one is built to outlast it. Backed by the Mishimoto Lifetime Warranty, this Performance Aluminum Radiator is the last cooling upgrade your 2012-2015 Honda Civic Si will ever need.

• 63% more core volume over stock — the enlarged core delivers greater surface area and thermal capacity than the factory unit, running measurably cooler when the K-series is pushed hardest.
• All-aluminum construction, no plastic to crack — full aluminum end tanks joined by precision TIG-welds replace the factory components that fail under heat cycling and sustained high-rpm use.
• Built for the high-rev demands of the Civic Si K-series — the oversized aluminum core absorbs sustained thermal output during back-to-back pulls, spirited street driving, and track sessions where the stock radiator begins to fall behind.
• Drops in without modification — confirmed direct fit for the 2012-2015 Honda Civic Si, compatible with all stock hoses and components — no cutting, fabricating, or adapter work required.
• Included high-pressure radiator cap maintains optimal system pressure — delivers enhanced cooling performance from the first drive without sourcing additional components.
• Magnetic drain plug removes ferrous debris before it circulates — catches metallic particles from the cooling system to protect K-series engine internals and extend service life beyond the stock interval.
• Own it for life — backed by Mishimoto's Lifetime Warranty, your investment is protected long after install day.