Oil coolers


Automotive oil coolers are a form of insurance to keep your car or truck new and to avoid expensive repairs.

OE manufacturers build their vehicles for "normal" use! Well, you don't do normal now, do you? As a "lead-foot" you know that hot laps around a racetrack, rock climbing, spirited driving, towing, or repeated passes at the drag strip have nothing to do with normal driving. There, the event can exceed your original equipment manufacturer’s engine or transmission oil cooler duty cycle, and it becomes overwhelmed with the dreaded heat soak syndrome.

What does an automotive oil cooler do?

An automotive oil cooler is a radiator-like device tasked with keeping the temperature of a lubricant within a predetermined range that reflects the optimum operating temperature for the type of oil used in the system.

Tow, haul, hot weather, stop and go traffic, hills, racing, or stump on the gas and your car or truck is a candidate for an engine oil cooler, transmission, gearbox, differential, power steering, and in racing a valve spring cooler.

Jeep oil cooler
Off-road cars and Jeeps need coolers for the engine, transmission, differential, and power steering. Large rocks and factors like snow or mud cause wheel spin, and sand creates drag; those elements necessitate additional throttle pressure (power) to overcome. Heat is power, and power is heat.Photo courtesy of Jeep 4X4 School.

"Preparation is essential in off-roading. Something as simple as the lack of an oil cooler can cost you a transmission, and or  an engine, not to mention being stranded miles from civilization." Don Alexander, Jeep 4X4 School Chief Instructor

Effect temperature oil viscosity EArl's

Joe Gibbs Racing Oil's chart above displays the  amount of loss of viscosity by engine oil when it is heated. The threshold is avoided with an adequate oil cooler in sufficient air stream. 


OEMs manufacture their oil coolers, for transmissions or engines, for "normal" driving and "normal" conditions! collaborates with the best manufacturers and their technical advisors. For oil coolers, fittings, lines, hoses, pumps, and cooler gaskets, we deal with C&R RacingAFCO, Earl's, and B&M Racing. Earl's and B&M are divisions of Holley. Bryan Grigsby, Holley's Motorsports Technical Advisor, assisted with this article.

Bryan explained:

"The first thing you have to remember is that power is heat! As soon as an engine crosses its threshold of power, the oil overheats and must be cooled. Contrary to common knowledge, oil coolers do not cool lubricants, but oil coolers aim to maintain oil temperatures (possibly with the aid of an oil thermostat, ed) within a predetermined range ideal for the lubricant used in the system. Considering that oil loses half its life for every 20 degrees in excess heat, it becomes evident that lubricants must be kept in check."


An ounce of prevention!

As soon as an engine crosses its threshold of power, the oil overheats, and it loses some of its original viscosity!  Avoid expensive damage to your hard-earned high performance engines and drivetrain components with the best automotive oil coolers for engines, transmissions, gearboxes, transaxles, differentials, and power steering units.


Prevent costly breakdowns with better flow and reliability!

Engine and transmission oil coolers need the best flow possible. Upgraded coolers replace marginal ones with higher cooling capacity and enhanced design for improved reliability to prevent cooler leaks and to maximize the cooling ability. Performance enthusiasts and race drivers prefer the Stacked Plate design automotive oil coolers.

Failure to correctly choose an oil cooler assembly can cause expensive and possibly hazardous results from a simple cooler leak to a ruined engine, transmission, differential, or power steering unit.

oil cooler for motorhome
Whether you race a NASCAR Cup Car or you drive a motorhome, you must keep a watchful eye on the engine and transmission oil temperatures. Motorhomes and RVs are massive, and their frontal area creates heavy air resistance. A trailer only adds to the need for additional cooling.


Buy a cooler that is Purpose-Made or pay the price later!

OEMs manufacture their oil coolers, for transmissions or engines, for "normal" driving and under "normal" conditions. If you need an engine oil cooler, buy one made to cool engine oil. If you need a cooler for a manual transmission or differential, get one made purposely for those applications.

oil cooler for street rods
Street Rod engines typically produce large amounts of power. They often sit idling at car shows or at "Cruise Nights"; they may drive slowly in traffic. All those parameters create a "perfect storm" for overheating an automatic transmission and engine oil. Coolers with fans are helpful in those conditions. Some Street Rods race on weekends, and they use high stall speed torque converters that cause the engine to rev up off the line. "Power is heat, and heat is power."

Several parameters enter the equation when designing purpose-made oil coolers.

  • The best coolers purpose-made for thicker lubricants such as gear oil and differential fluid require more significant passages and fittings as well as a larger surface area to facilitate flow and reduce back-pressure. Oil cooler manufacturers recommend installing an oil thermostat when operating in cold weather.                                                                
  • The best (correct) oil coolers used for automatic transmissions and power steering units are purpose made and they have smaller tubes and inlets because the fluids used in those units are relatively thinner. In this case, the oil lines and their fittings can also be of smaller size.                                                                                                                 
  • Manufacturers of the best oil coolers research and test airflow through their coolers to maximize heat rejection. The cooling fins are of proprietary design, and they have undergone extensive testing in wind tunnels. 
Earls oil cooler Healy
Professional engine builders and racers use Earl's oil coolers on cars like this four-cylinder Austin Healey Sprite and V8 racing cars. Even small automobiles may also require gearbox coolers and pumps.


  1. 220-240 F – Varnish forms on internal components.
  2. 240-260 F – Transmission seals begin to harden and leak.             
  3. 260-295 F – Clutch plates start to slip and create added heat and abrasive materials in the fluid.                                   
  4. 295-315 F – Seals and clutches burn-out. The transmission sustains catastrophic failure.
oil cooler road racing
Performance enthusiasts, race cars, and truck drivers use engine oil coolers, transmission coolers, differential coolers, automatic transmission coolers, and power steering unit coolers. In some forms of racing, they use valve spring coolers. photo


An oil cooler becomes necessary when any component of the drivetrain surpasses its threshold of power.
  • High ambient temperatures are probably the most significant cause of overheated lubricants.
  • Any condition that requires additional power like with hills, headwinds, towing, and hauling a load affect lubricant temperatures.
  • Tailwinds reduce the air intake through the radiator and coolers.
  • Stop-and-go driving requires repeated accelerating and slowing. Accelerating from a stop is one of the most power-demanding actions on a car or truck.
  • Increased torque converter stall speed requires more aggressive throttle application and higher engine RPM to create more power.
  • An increase in engine power, produces more significant amounts of heat.
  • Wheel spin, like in rain, mud, or snow, makes the transmission and the engine work harder.
  • Transmission or engine malfunctions can also create undue amounts of heat like with slipping clutches, blown head gaskets, improperly adjusted throttle valve cable and vacuum leaks.
Oil coolers dirt car
In Oval Dirt track and off-roading, mud and debris can be an issue in cooling. Here is an example of where an oil-to-water cooler is beneficial. Proper planning and perhaps over-building the cooling system favors the winners.


There are oil coolers for engine oil, transmission fluid, power steering systems, gearboxes like race car manual transmissions, differentials, and even race car valve springs. These oil coolers find their way on cars, trucks, vans, SUV s, motorhomes, RVs, race cars, Street Rods, Muscle Cars, Jeeps, sports cars, tow-vehicles, emergency vehicles, four-wheel drives, 4X4s, high performance vehicles, and many more.
Oil cooler applications
This chart shows which components require a cooler for a specific application. The legend at the bottom explains the terms. Upgraded oil coolers are vital in maintaining your vehicle's performance and in preventing expensive failures. 


Choose the right cooler for your application

Use coolers purpose made for differentials and gearboxes for engine oil, transmission, power steering, and valve spring cooling. Their fittings and tube dimensions are sufficiently large to avoid most pressure drop.

Coolers for engine oil, transmission, power steering, and valve spring cooling do not have sufficient flow capacity to permit the use of thicker fluids like gear lube. Choose smaller coolers for power steering and valve springs.

oil coolers
Most oil coolers are of the air-to-oil type. They also usually have their fittings coming out the top. The larger coolers sport bigger fittings to allow them for use on thicker fluids like gear lube.
deck mount oil cooler AFCO appliedspeed.comSome coolers, called "Deck Mounts" (right), have flanges that permit installing them directly into a panel. The fittings come out the back or the sides to facilitate plumbing. Deck Mount coolers are very thick, and as such, they should mount in the full airflow, and on fast cars to allow the air to saturate the matrix thoroughly. oil to water cooler C&R Racing For auto racing and off-roading, some coolers are of the oil to water type (left), where water passes through a canister that contains the oil cooler tubes and fins. These coolers are handy when access to free flowing air is not available and they tuck away from rocks, mud, and crash damage.
"Oil coolers are a form of insurance."
Jean Genibrel Tech Editor
Early Camaro oil coolers AFCO B&M AppliedSpeed.comNew or old. Chevy or Ford. Muscle Car or race car. They all need some attention with engine oil cooling and transmission temp monitoring. Older Muscle cars had marginal cooling systems, and many Hot Rodders further increase the power of their ride, necessitating an upgrade in the temperature maintenance department from the engine to the differential. Late Mustang Earl's oil coolers AppliedSpeed.comMuscle Cars can go into "limp mode" due to excess heat and substandard coolers. These cars benefit from aftermarket engine and transmission coolers. Some sport a supercharger, and there a heat exchanger assists in maintaining temperatures at an acceptable level and performance at its peak. 


Major features include:

  1. Stacked Plate coolers are up to 30% more efficient than any other design.
  2. Highly developed fin design produces a boundary layer that maximizes heat dispersion.
  3. The correct size coolers have nearly zero flow restriction resulting in maximum cooling efficiency and pressure drop.
  4. They are vacuum brazed for maximum reliability.
  5. Stacked Plate coolers are the most efficient and sturdiest of the coolers.
  6. They are available in many dimensions and with the correct size fittings to allow free flow.
  7. The internal passages feature turbulators to swirl the fluid against the interior tube surfaces.

  AFCO, B&M, C&R, SETRAB, and Earl's' coolers for transmissions, engine, gearboxes, power steering, and differentials feature a Stacked Plate design, which is up to 30% more efficient than other models. When chosen correctly, they have nearly zero flow restriction.

Earl's stacked plate coolers
earls's stacked plate cooler 41916ERL appliedspeed.comStacked Plate coolers have tanks on each side of the units to minimize back pressure and unify the flow of the oil over the whole tube group. This design provides strength to the units while reducing weight. The side tanks afford an ample supply of oil to the tubes as well as an even oil distribution. This engineering design avoids hot and cold spots to maximize cooling potential as well as to reinforce the cooler.

Oil-to-Water Oil Coolers

Oil-to-water coolers use the engine water to cool the oil. The unit consists of a canister that contains the oil cooler. The cartridge is sealed, and freshwater from the radiator passes through the oil-to-water cooler to absorb the excess temperature from the oil.

oil to water oil coolers C&R AFCO
The oil-to-water concept allows the drivers to install the coolers out of harm's way from mud, rocks, and crash damage. The canisters install directly in the cold radiator hose with standard hose clamps.
The cooling air that passes through the car grill can increase by two to four times its original volume from the heat it has gathered through the coolers. The increase in volume creates pressure under the hood, and it prevents fresh air from entering the radiator and coolers. Dodge created these vents on their new Viper sports cars to relieve the pressure from under the hood. This modification helps to reduce the temperature of the engines and transmissions. 


The best oil cooler is the one that is purpose-made for your intended application. Racing, trucks and towing, off-roading, Street-Rods, Jeeps even motorhomes can benefit from the right cooler. 

There are oil coolers made for engine oil, automatic transmission fluid, gearboxes like those used in racing, differentials, power steering fluid, and some forms of racing call for cooling the engine valve springs.

 Stacked Plate coolers are the highest quality, and they h

B&M Super Cooler Oil Coolers 70268
B&M's transmission coolers are available in several sizes to satisfy all possible choices, from racing to motorhomes. Displayed is a kit that contains all the parts to install a transmission oil cooler in everything from an off-road Jeep to a motorhome. Photo B&M Racing

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