How to Choose the Right Mocal Oil Cooler for Your Car

Keeping your engine oil at its proper design temperature is one of the most critical factors for vehicle longevity and performance. If your oil gets too hot, it becomes thinner (less viscous) and loses its vital film strength. Supported by oil pressure, this film strength is what keeps moving bearing surfaces from touching.

Once bearing surfaces make metal-to-metal contact, friction quickly removes material, clearances widen, oil pressure drops, and catastrophic engine failure takes place. Furthermore, in modern engines where oil is used to cool the piston crowns, overheated pistons can cause detonation, massive power loss, or complete piston and gasket blowouts.

As a general rule, oil temperatures in excess of 110°c should be avoided. If you are hitting the track, towing, or running a modified setup, a high-quality oil cooling system is essential.

In this guide, we will break down why oil temperatures spike, how to choose the right core technology, and how to install your cooler for maximum efficiency

Why Do You Need an Engine Oil Cooler?

The factory setup on most standard cars ensures just enough cooling via natural airflow across the oil sump to keep oil at its ideal temperature during normal driving conditions. However, changes to your vehicle's specifications or how it is driven will quickly cause oil to exceed safe limits.

The primary causes of dangerous oil temperature increases include:

• High RPM and Track Use: This is the most common cause of engine oil overheating. An engine's oil cooling requirement can increase up to threefold for an increase of just 1,000 RPM. On a race track, the constant use of high RPM makes an oil cooler mandatory, even for an unmodified engine.
• Turbochargers: Oil circulating through a turbocharger does not just provide lubrication; it also removes a massive amount of concentrated heat from the turbo housing, heavily increasing the overall cooling requirement.
• Airflow Restrictions: Modifying your car by fitting low spoilers, body kits, or heavy-duty sump guards can block the vital stream of air designed to cool the oil pan.
• Increased Power Output: Boosting your engine's horsepower will naturally increase combustion temperatures, adding more heat stress to the entire system.

Beyond the Engine: Cooling Gearboxes and Drivetrains

Oil coolers are not just for your engine block. They are highly effective for cooling gearboxes, crown wheel and pinion units, differentials, and power steering pumps.

With drivetrains and steering gear, the goal is less about preventing instant metal-to-metal contact and more about preventing a loss of component tolerances due to heat expansion. When internal metals expand from excessive heat, it creates greater friction, triggering a rapid, runaway spiral of heat buildup.

• On the Road: The most common drivetrain issue occurs with automatic transmissions when vehicles are used for heavy towing. While many vehicles feature factory transmission cooling, it is usually inadequate for heavy loads. Adding a dedicated cooler is crucial because higher operating temperatures quickly destroy rubber seals, which can be as expensive to replace as an entire gearbox.
• On the Track: Track racing leads to significantly higher drivetrain temperatures due to extreme power loads, constant gear shifting, wheelspin, and aggressive steering activity.
  

Pressed Plate Oil Coolers

The most popular and efficient option for automotive applications is the pressed or stacked plate cooler. First engineered in the late 1950s, this design beautifully balances simplicity with heavy-duty performance

• How it Works: The cooler consists of a variable number of aluminium pressed plates that form uniform oilways and end tanks. The internal oilways contain turbulators, which break down the boundary layer effect in the fluid flow. This ensures maximum heat dissipation without causing an undue drop in oil pressure.
• Why it Lasts: Because all components are brazed together under intense pressure, the core acts as a single, structurally sound unit. This makes it an incredibly robust and mass-production-friendly option for everything from fast road cars to dedicated track builds.

Sizing Your Oil Cooler

When choosing a cooler size, heat dissipation is not the only parameter to look at. A larger cooler is often selected purely to avoid an excessive drop in oil pressure.

As a general engineering rule across oil cooler designs: the more rows or tubes the cooler has, and the shorter their overall length, the smaller the internal oil pressure drop will be. Maximum working pressure on the standard range of coolers is 10 bar (150psi), which is adequate for all but the most arduous motoring applications.

Why use an Oilstat (Thermostat) for Street Cars

While keeping oil cool is vital, running an engine with oil that is constantly too cold is equally dangerous.

Prolonged driving in conditions where the oil cannot reach its proper working temperature causes rapid sludge formation and crankcase oil dilution, leading to severe, accelerated wear on the cylinder bores. Cold oil also creates internal engine drag, which saps horsepower. Everyday road cars use multi-grade oils formulated to handle ambient extremes, but they still require a minimum heat threshold to perform optimally.

By installing a thermostatic bypass device - an Oilstat - the oil flow is automatically managed:

• The Oilstat prevents oil from entering the cooler core until it reaches 80°C.
• This 80°C target is the minimum temperature required to safely evaporate and dispel water and fuel contaminants from your oil system.
• Once up to temperature, it permits a low-viscosity oil to flow freely, maximising engine power and decreasing fuel consumption during relaxed driving.

Installation Tips for Maximum Efficiency

An air-to-oil cooler relies entirely on a high volume of ambient air passing directly through its external cooling fins. The amount of heat dissipated by raw radiation alone is negligible. Use these placement and mounting rules to get the best results:

Perfect Placement & Ducting

• In Front of the Radiator: The most effective and convenient position is directly in front of the vehicle's water radiator, where a steady flow of high-velocity air is guaranteed. Because of the sheer volume of air moving through the vehicle nose, the air passing through the oil cooler is only heated by a few degrees - meaning it will have virtually no negative impact on your main water radiator's performance.
• Sealing the Face: If your engine's water cooling is already marginal, the oil cooler must be mounted flush against the water radiator face. If there is a gap between them, the warm air exiting the oil cooler will become turbulent when it hits the ambient air gap and fail to pass through the radiator. If you cannot mount them flush, you should fabricate a thin aluminium duct shroud to completely enclose the space between them.
• Rear Mounting: If an electric cooling fan blocks the front of your radiator, the oil cooler can be securely mounted behind the water radiator and will still function highly efficiently.
• Repositioning the Grille: If space is tightly limited on both sides of the radiator bulkhead, you can often gain clearance by moving the exterior radiator grille slightly forward using longer mounting screws and custom spacers. Alternatively, clean air ducts can be cut into the forward bulkhead on either side of the main radiator to channel fresh air directly to a remotely hidden core.

Secure Mounting & Plumbing

• Bracket Limits: Standard universal mounting brackets are highly effective. Mounting your cooler using only the bottom brackets is perfectly fine for cores up to 13 rows. For any core larger than 13 rows, you must use all 4 mounting brackets, utilising long bolts and matching spacers to spread the heavy weight and structural load evenly.
• Vibration and Heat Expansion: Oil coolers physically expand when they get hot. Because the built-in brackets are the weakest part of a plate-style cooler, vehicle vibration or mounting platform twisting can cause them to snap, which frequently ruins the entire cooler. If your vehicle is subject to extreme vibration, consider abandoning rigid brackets entirely. Instead, mount the cooler inside a protective cradle or secure it using heavy-duty cable ties or an elastic strap. The heavy oil hoses themselves will naturally provide a baseline level of structural restraint.
• Orientation: Air-to-oil coolers can safely be mounted in any orientation (ports facing up, down, or sideways). Because the internal flow resistance through the dense matrix is perfectly uniform, the end tanks will fill up evenly, making the entire cooling system completely self-bleeding by pushing out air ahead of the oil flow.