Oil Temperature Maintenance for Cars, Trucks, Off Roading, Jeeps, Racing, and Motorhomes

 By Jean Genibrel 08-30-2013
Need to Manage the Temperature of Engines, Transmissions, Differentials and Power Steering Systems.

Slow driving with large tires place an added stress on the power steering and the transmission fluids as well as the engine oil. This Jeep is a real candidate for oil coolers, shrouds, and electric fans.

To be perfectly accurate we should use the term “thermal management” instead of “cooling.” Water and lubricant temperatures first need to come up to working temperature. Maintaining component temperatures via the coolant and the oil within an acceptable level is primordial in automotive engines, transmissions, differentials and power steering systems to ensure their longevity, reliability, and consistency. Elevated or overly reduced oil or water temperatures affect performance and reliability. The use of coolers, ducts, and shrouds with remote mounts achieve temperature control in automotive fluids. Other devices that need thermal management include engines in forklifts, tractors, irrigation pumps, concrete pumps, welding equipment, and air compressors.

Racers and heavy duty equipment operators use oil thermostats to allow the oil to heat up quickly to avoid loss of pressure and to save time getting out on the road.Water thermostats remain shut until the coolant temperature.
The purpose of a thermostat is to bring the water up to normal operating temperature more rapidly. 

Fast warm up in a passenger or performance car reduces fuel consumption as engines use more fuel when cold. Thermostats allow the circulation of fluids at a predetermined temperature. Thermostats permit the temperatures to increase to their normal operating range, and then they open to prevent overheating.

water thermostatWater thermostats remain shut until the coolant temperature rises to the level that  the thermostat was set. Generally thermostats are set to open at 175 to 185 degrees Fahrenheit.

Manufacturers utilize a water and glycol mixture to cool the top end of engines. In the lower end, to avoid damaging the components and to maximize their life expectancy, manufacturers use engine oil. In manual transmissions, transaxles and rear ends they install oil that is much thicker and of a different chemistry than the variant used in engines. Automatic transmissions use automatic transmission fluid (ATF). Both types of lubricants come in the mineral kind and the higher quality synthetics. In racing, coolant and fluid temperature variations can affect consistency and repeatability in lap times and ETs. Automatic transmissions can use automatic transmission cooler and fans. ATF cannot be overly cooled, so there is no need to be stringent with the coolers used.

Fans and shrouds are available through APPLIEDSPEED.COM. These can be used to cool transmissions, power steering units, and engine oil.


Stacked plate coolers are the most efficient and sturdiest of the coolers. Those are real racing coolers, but they are also used on performance cars and trucks, for engines, manual and automatic transmissions, differentials and power steering units. The best coolers  are brazed.

APPLIEDSPEED.COM offers a complete line of coolers, fans, and shrouds for direct fit applications such as for Jeeps and universal fits for cars, trucks and motor-homes. Fan, shroud and coolers such as this one are ideal for transmission and power steering cooling. For off-roading, racing, trucks, jeeps and more.






In the past few decades economic and environmental conditions have combined with technological advances to change the modern vehicle dramatically. These changes challenge the design of every part of a vehicle. These conditions have made it imperative to manage and monitor water and lubricant temperatures more closely in automotive components. Engines are more efficient, and they produce more heat than those of earlier years. They turn higher RPM and their increased torque places an additional load on transmissions and rear axles. Also, manufacturers and hot rodders often use forced induction with turbochargers or superchargers. These devices further increase under hood temperatures, and they place additional stress on the cooling systems from their increased power output. Vehicles in need of improved cooling include high-performance and muscle cars, race cars, off-road vehicles, heavy-duty tow and commercial vehicles, motor homes and vehicles with increased trailer towing capacity. 

Increasingly stringent emissions standards place an additional burden on engine oil as it is also called upon to prevent gasses from bypassing the rings. To further improve emissions, engine manufacturers reduce clearances at the piston skirts and the engine bearings down to the range of two thousands of an inch (.002”). Consistent oil and fluid temperatures are essential in maintaining the correct viscosity to provide the cushioning and to reduce friction in all the vehicle’s components. Oil temperature affects oil viscosity which in turn affects the oil’s ability to cushion pressure on engine bearings and at the cam and lifter interface.


Plate and fin coolers include internal turbulators to swirl the fluid against the plates for maximum efficiency. These are used on engines, transmissions, rear ends and power steering units. Furnace brazed aluminum construction ensures durability.

Some engines use variable valve timing (VVT) which operates on engine oil pressure. These systems offer huge advantages in reduced emissions and fuel consumption and torque increases at all engine speeds. However, VVT has engendered some specific issues in the realms of lubrication and diagnostics. Technicians can at times trace these matters to the oil temperature and its effect on viscosity since oil pressure has a direct effect on the cam phaser that controls camshaft timing.

What is more, the engine oil is called upon to cool the valve springs which are nothing more than metal bars that are bent thousands of times a minute. Valve springs remain the highest source of oil temperature in a racing engine. In manual transmissions and differentials, the oil cushions the shock between the teeth and it eliminates metal contact at the gears.


Tube and fin coolers are intended for automatic transmissions and power steering units. The tubes are too restrictive for engine oil, manual transmission or rear axle lube, especially in colder climates. Their cooling efficiency is relatively low so they require a much larger effective surface area to approach an adequate temperature drop. As such, the money savings the motorist may enjoy will be negated by the amount he will have to spend on a cooler of adequate size. These units are derivatives of the heating and cooling industry where they are kept in vibration-free environments and steady temperatures.

Automatic transmissions pressurize their fluid to operate the clutches. Pressure creates heat. If the fluid temperature becomes elevated, its viscosity falls with an associated loss of pressure. The lower pressure on the clutches causes them to slip, and they eventually fail. Excess heat causes the seals to harden and create leaks that cause pressure drop and leakage.


Jeep 4X4 School made their Jeep JK with big Falken tires available to us and we exaggerated some settings like the toe-out to show the need for a power steering cooler. Then we loaded the front of the radiator with accessories to display how easily airflow can be obstructed. Several parameters can elevate the power steering fluid temperature to where a cooler and possibly a fan become imperative. Larger wheels and tires, high caster and scrub radius settings on the front end, and any condition that requires continuous turning cause excess heat. Racers will recognize the first two conditions, and off-roaders can identify with the others, particularly Rock Crawlers and Dune Warriors.

 APPLIEDSPEED.COM is the website that sells performance and racing cooling parts for all disciplines of racing. From circle track to road racing, autocross, off-road racing, drag racing. Further, addresses the needs of racers for their tow vehicles with products such as oil coolers for engines, transmissions, power steering and differentials. Also serviced include motor-homes, industrial engines, and Jeeps.

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