Mishimoto Performance Auxiliary Radiator BMW F8x M3/M4 S55 2015-2020 - Fits Either Side

The S55 in the F8x M3 and M4 leans on a pair of auxiliary radiators mounted low in the front corners of the car. They sit in the worst place on the vehicle - first in line for road debris, and low enough that their plastic end tanks crack after enough heat cycles. This Mishimoto unit replaces one factory auxiliary radiator with an aluminum core carrying 9% more volume and 32% more external tube area than stock, so it rejects more heat and recovers faster between hard runs.

The single-row core is 1.6 inches thick with strutted tubes to resist the vibration and stone strikes that fatigue a low-mounted radiator, and aluminum TIG-welded end tanks replace the factory plastic ones. A removable powder-coated steel stone guard shields the exposed face. One radiator ships per box, and the bracket design fits either the driver-side or passenger-side auxiliary radiator location, so the same part number covers both positions - order accordingly for the position or positions you are replacing. It is a direct fit in the factory auxiliary radiator location with no cutting, fabricating or adapters, and it is backed by the Mishimoto Lifetime Warranty.

• 9% more core volume and 32% more external tube area than the factory auxiliary radiator
• Aluminum core with strutted tubes and TIG-welded aluminum end tanks - no plastic tanks to crack
• Removable powder-coated steel stone guard protects the exposed core face
• Single bracket design fits both the driver-side and passenger-side auxiliary radiator locations
• Single-row core, 1.6 in thick
• Direct fit in the factory auxiliary radiator location - no cutting, fabricating or adapters
• Box contains (1) auxiliary radiator, (1) stone guard, (2) mounting brackets, (3) O-rings, (8) M6 lock washers and (8) M6 button head bolts
• Mishimoto Lifetime Warranty

Specifications

Documents: Installation Instructions (PDF)

This part fits:

Shipping

• In-stock orders placed before 3 PM EST ship the same day — everything else ships within 24 hours.
• Standard, expedited, and overnight options at checkout.
• Oversized items ship by freight and take longer.
• Backordered items ship as soon as stock lands — contact us for lead times.
• International orders: prices do not include VAT, duties, or import fees. Your country charges these at import and they are the buyer’s responsibility.

Returns

• 30-day returns on new, uninstalled items in original packaging with all hardware.
• Standard returns: 8% restocking fee, buyer pays return shipping. Both waived if the item is defective or we made the error.
• Installed or used parts can’t be returned — confirm fitment before you install.
• Special orders and custom items are final sale.
• Email us for return authorization before shipping anything back.

Full details: Shipping Policy · Refund Policy