Oil and Fluid Coolers

Is the temperature of your engine oil, gearbox oil or power steering fluid creeping up during track days, towing or hard driving on country roads? This category brings together oil coolers, complete kits, transmission coolers, power steering coolers and thermostats that can keep the fluids within a stable temperature range. It is for you if your project puts more strain on the engine and drivetrain than normal.

What an oil or fluid cooler does

Oil lubricates and at the same time carries heat away from bearings, pistons and gears. If it gets too hot, its viscosity can drop, so the lubricating film becomes thinner and the oil breaks down faster. An external cooler routes the oil through a cooler core in the airflow. For the engine there are engine oil coolers and complete oil cooler kits with hoses and adapter, while transmission coolers are used for automatic and dual-clutch gearboxes, e.g. the CSF DCT Oil Cooler for the BMW M3. The power steering can also overheat on track, and here a power steering cooler can relieve the strain on the fluid.

How to choose the right cooler

• Cooling capacity: depends on the core design, e.g. dual-pass, and on the airflow through it – not just on its size.
• Pressure drop: a dense or long core can create resistance, especially with cold oil.
• Space: measure up so the cooler gets fresh air without blocking other coolers.
• Connections: check threads and fittings, e.g. -10AN or OEM connections.
• Vehicle-specific or universal: a universal cooler with stated dimensions requires more fitting work than a model made for your exact car.

Brands in the category include Mishimoto, GReddy, HKS, Perrin Performance and CSF.

Thermostat, installation and maintenance

The oil also needs to reach its operating temperature. An oil cooler thermostat typically only opens to the cooler once the oil is warm, so it doesn't get overcooled in cold weather. Position the cooler so it doesn't steal too much air from the radiator, and route hoses away from the exhaust manifold and moving parts. Check connections and oil level after the first few drives, and clean dirt and insects off the cooler core at regular intervals.

Frequently asked questions

Should I choose a complete kit or a standalone oil cooler?

A kit typically contains the cooler, hoses, fittings and adapter, so the parts match each other. A standalone cooler gives you freedom to build your own setup, but requires you to choose connections and hoses that suit your car yourself.

Why use a thermostat with the oil cooler?

Without a thermostat, the oil can get too cold on short trips or in winter. The thermostat typically routes the oil past the cooler until it is warm, so the engine reaches its operating temperature faster.

What should I check after installation?

Run the engine up to temperature and look for leaks at all joints. Check the oil level, as the cooler and hoses hold extra oil, and retighten the connections after the first few drives.

When can a power steering cooler be relevant?

During long track sessions or a lot of steering work, the power steering fluid can get hot, so the steering may feel uneven. Whether a cooler helps depends on the car's system and how you drive.