CSF Race-Spec Oil Cooler - BMW 135i/ M135i

N55-powered BMWs have become a favorite among track and performance drivers — but maintaining optimum oil temps is key to avoiding "cool down" laps and limp mode. Building on their proven BMW cooling expertise, CSF developed this upgraded oil cooler specifically for the N55 platform.

Using AC Condenser Technology, this innovative dual-core in-series system adds 5 rows of super-high pressure multi-channel microtubes on the rear side of the cooler. Combined with a high-efficiency multi-louvered fin design, it delivers ~40% more heat rejection than the factory unit — keeping oil temps consistent and manageable even under extreme, extended driving conditions.

It's a true drop-in fit, accepting all factory oil-line connections, mounting brackets, and shroud/ducting — no modifications required. Note: the added capacity increases total oil volume by 0.5 qt. (7.5 qts. vs. OEM's 7 qts.), so plan for the extra oil at install.

Features

• Innovative 2-core in-series cooling system
• Front core with 14 rows, secondary backside cooler adds 5 more — ~40% increase in heat rejection
• Converted to single-pass design with high-pressure return line for optimal flow
• CSF AC Condenser Technology — 1-row, super-high pressure 26mm multi-channel microtube
• High-density, multi-louvered fin design for max surface area contact
• Drop-in fit, no modifications, accepts all OEM connections and hardware
• World's first true plug-and-play upgraded oil cooler for the N55 engine
• Track tested and proven by Hittman Racing's M235i endurance race car
• Requires 0.5 qt. additional oil at fill-up (7.5 qts. total)

Fitment