The FL5 Civic Type R quickly proved itself on track, but one weakness became obvious under sustained hard driving: engine oil temperatures. Even in stock form, oil temps regularly climb beyond safe limits, and modified examples only exaggerate the problem. During real-world testing, CSF recorded oil temperatures exceeding 275°F (135°C), making it clear that a comprehensive solution was required.

To address this, CSF developed its first complete engine oil cooler system for the FL5. Rather than a compromise add-on, this kit was engineered from the ground up to deliver reliable oil temperature control in the harshest track conditions, while maintaining OEM-level fitment and a motorsport-inspired appearance.

One of the biggest challenges was airflow. With the intercooler, A/C condenser, and radiator already stacked behind the front grille, adding another heat exchanger in that area would reduce overall cooling efficiency. Instead, CSF designed a dual oil cooler system mounted in the bumper sides, paired with dedicated carbon fibre ducting to deliver consistent airflow directly to the coolers without affecting the main cooling stack.

The system uses two CSF dual-pass oil coolers run in series, providing maximum heat rejection while maintaining durability. These are the same core designs trusted by Honda Racing Corporation on factory touring car programs. Combined with motorsport-grade AN lines, quick-release fittings, and a thermostatic billet sandwich plate, this is one of the most serviceable and effective oil cooler kits available for the FL5 platform.

Testing across dyno sessions and multiple track environments showed consistent reductions in oil temperature, with average drops of 15–20°F and peak reductions exceeding 30°F in extreme conditions. Importantly, the system maintains safe oil pressure by pairing the cooling system with appropriate oil weight recommendations for track use.

Key Features:

Dual high-performance CSF oil coolers mounted in series for maximum cooling capacity
Dedicated pre-preg carbon fibre bumper vents designed using CFD analysis
Laser-cut mounting brackets and louvered fender liner vents for efficient heat extraction
Billet aluminum sandwich plate with integrated 175–195°F (80–90°C) thermostat
Motorsport-grade stainless steel braided lines with quick-release fittings
Increased overall oil capacity of approximately 7 quarts (6.6L)
Replacement washer fluid reservoir to free bumper space while retaining factory pump

Notes regarding Oil Pressure Drop

When adding an engine oil cooler to a car that did not come with one from the factory, there is always a concern with pressure drop. This is due to the back pressure imposed on the system from running the oil through lines and cooling channels of an oil cooler.

In testing, CSF observed a small drop in oil pressure after installing the kit. While not a concern for casual driving, it was enough of an issue to address for those tracking their FL5s. To resolve this issue, CSF and test vehicles switched to a higher weight oil (from OE Spec 0W-20 to 0/5W-30) and this relieved the potential pressure issues.

Metric	Stock with 0W-20 Oil	CSF with 0W-20 Oil	CSF with 0/5W-30 Oil
Idle Operating Temp	20 PSI (1.4 Bar)	15–17 PSI (1.0–1.2 Bar)	20 PSI (1.4 Bar)
On Track – Straight	70 PSI (4.8 Bar)	50 PSI (3.4 Bar)	67–69 PSI (4.6–4.8 Bar)
On Track – Corners	59 PSI (4.1 Bar)	47 PSI (3.2 Bar)	56 PSI (3.9 Bar)
Highway Cruising	75 PSI (5.2 Bar)	55 PSI (3.8 Bar)	70 PSI (4.8 Bar)

CSF recommends the following oil weights depending on application:

Light Track Duty and/or High Performance Street: 0/5W-30
Heavy Track Duty and/or Dedicated Race Builds: 0/5W-40

Oil Coolers

The CSF kit is built around two 13” x 4.5” (33cm x 11.5cm) Dual-Pass Oil Coolers (CSF #8119) run in series. These High-Performance Coolers offer maximum heat dissipation with uncompromising durability. The Bar/Plate cores feature CSF’s “Aero-Flow” Bar Design which reduces weight while offering impressive strength and flow. The rugged design of these cores means you won’t need to worry about debris from the track puncturing the coolers like with tube and fin cores.

The 100% TIG welded construction with cast end tanks further increases the overall strength of the coolers. Every cooler is pressure tested to 120 PSI before leaving the factory so you can be confident you will never have one burst on you like some weaker designs used in other kits. The end tanks also feature specially designed 40-degree angle feed/return fittings for optimal flow and lower pressure drop.

Oil Cooler Details:

Dual-pass bar and plate core design for strength and thermal efficiency
100% TIG-welded construction pressure tested to 120 PSI
40-degree feed and return fittings to reduce pressure drop
Over 2 quarts (2 litres) of additional oil capacity

The are the same coolers Honda Racing Corporation (HRC formerly HPD) uses on Honda’s factory FK8 TCR Touring Car. Honda and many racing teams/drivers saw a lot of success with the FK8 Type R TC. CSF is already working with teams like Precision Racing LA for their FL5 Touring Race Car and in talks with other SRO teams and HRC themselves.

Lines, Fittings, and Thermostat:

CSF partnered with DYME PSI again for their exceptional quality and innovative quick-release hose and fitting solutions. The DYME Pro/Spec Quick Release Fittings offer race-proven performance with the convenience of tool-free clamshell removal and capable of withstanding up to 10,000 PSI. Quick Release fittings make the installation of the CSF kit much faster than traditional threaded fittings. In addition, they make maintenance like fluid changes much less of a headache.

The DYME PSI fittings are hydraulically crimped to their motorsport quality Superstrasse CPE lined 304 stainless steel braided lines. DYME PSI manufactures these lines and fittings in house to CSF exact specifications with the highest level of quality and precision. These lines offer the best flexibility, flow, and chemical resistance possible.

Oil flow is managed by a Billet Aluminum thermostatic sandwich plate. This plate bolts in the factory oil filter location with a M20x1.5 adapter. The sandwich plate was designed to reuse the OE oil filter but can be fitted with a larger filter up to 70mm in diameter with a M20x1.5 thread (check height clearance when looking at filter options).

The thermostat is designed to start opening at 175°F (80°C) and be fully open at 195°F (90°C), great for motorsports and high-performance street applications. The sandwich plate also includes a pre-plugged 1/8 NPT port for aftermarket oil temperature sensors. This is a great addition for drivers looking for more accurate data/metrics.

Features:

Forged 6061-T6 aluminum quick-release fittings with 180-degree swivel capability
Dual fluorocarbon seals rated for continuous high-temperature operation
304 stainless steel reinforced braided lines with high burst resistance
Thermostatic control optimised for track and high-performance street use
Pre-plugged 1/8 NPT port for aftermarket oil temperature sensors

Ducting and Airflow Management:

The challenge of getting proper air flow to the oil coolers was straightforward but far from simple. While mounting an additional cooler behind the grill would be the easy choice, that just adds more heat to the rest of the cooling system. The optimal placement for the coolers was in the sides of the bumper outside of having no direct airflow. While technically some air does flow to this area as it leaks around the intercooler, it is not enough for significant cooling performance. While utilizing the brake cooling ducts is a potential option, that could negatively impact braking performance.

CSF designed and modeled vents for the bumper to provide the two oil coolers with ample airflow to keep engine oil temperatures in check. These vents were carefully designed with CFD software for airflow and aero dynamics. Made from pre-preg carbon fiber, these vents match the lines and style of the FL5 and give a very OEM+ look to the front bumper. To further improve airflow and cooling, the kit also includes louvered vents that allow airflow out of the bumper area and into the fender wells.

OE Fit and Finish

CSF leveraged many industry connections to find the best possible source for motorsport grade carbon fiber. The quality, fit, and finish of these parts are of the highest caliber and have been extensively track tested. Each vent bolts on without the use of double sided tape so they are very secure.

Cut out templates are included with the kit instructions to allow for easy installation and ensure proper alignment. CSF also designed templates for the international market with FL5s that come equipped with PDC sensors. The factory PDC sensors will still function perfectly and retain the OE look and feel.

While there may be kits available that do not require cutting the bumper, they cannot match the airflow and cooling performance of the CSF kit.

Features:

Motorsport-grade pre-preg 2x2 carbon fibre construction
OEM-style fitment with bolt-on installation (no double-sided tape)
CFD-optimised airflow paths for consistent cooling performance
Laser-cut louvered vents to promote heat extraction into the wheel wells

*Note: Carbon fiber vents can be refinished as in matte clear or painted. CSF recommends using a qualified paint or body shop for best results.

Replacement Windshield Washer Reservoir

To make room inside of the right hand side bumper for both the oil cooler and proper airflow, CSF designed a replacement windshield washer fluid reservoir. This low clearance reservoir/bottle works with the factory pump and filler neck. The engine bay retains a clean factory look while freeing up space in the bumper for the cooler.

Dyno Testing

For initial testing, CSF turned to the automotive authorities and industry experts at MotoIQ for third party verified data collection. Mike and the team there developed the testing procedures for the prototype baseline data.

Temperature readings were taken with two temperature sensors installed at the oil filter housing/sandwich plate for the most accurate readings. The FL5 was first run for 9 consecutive pulls on the dyno at World Motorsport to simulate hard driving and engine oil heat soak. The prototype CSF Oil Cooler Kit was then installed and the same test was conducted again. Average ambient temperature was only 0.5°F (0.3°C) higher on the test with the CSF kit.

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Extensive testing with professional drivers and Global Time Attack competitors confirmed consistent oil temperature control under extreme track conditions. With years of development and real-world validation behind it, this system represents one of the most comprehensive cooling upgrades available for the FL5 Civic Type R.

Engine/Transmission Oil System