The main functions of engine oil are lubrication, cooling and prevention of corrosion. If the condition of the oil deteriorates, wear and shortened service life will be the consequences. In the worst case, this can lead to engine damage if the engine is operated under excessively high oil temperatures. But the performance aspect should not be underestimated either: an engine can only deliver its maximum power at optimum oil temperature. Most production vehicles are designed without an oil cooler. In these cases, the air flow over the oil pan should be sufficient for oil cooling during driving. However, if the vehicle is now moved a little more sportily (i.e. primarily in the higher speed range), power is increased (as a rule of thumb, an increase in speed of 1000 rpm triples the cooling requirement of the oil) or the air flow is restricted (e.g. by fitting an underbody guard), then it becomes necessary to retrofit an oil cooler.
First of all, it is necessary to determine the design of the oil cooler. We distinguish between air-cooled oil coolers and water-cooled oil coolers. The air-cooled versions are by far the most common. Here, the oil cooler is placed in the airstream and the engine oil is directed through the cooler. For optimum efficiency, the cooler should be placed as far forward as possible, even before the water cooler. When arranged correctly, this has only a minor effect on the water temperature, as the enormous volume of air forced through the radiators ensures that the air temperature rises by a few degrees at most. Alternatively, you can think about a different arrangement with additional vents or ventilation hoses. The oil coolers themselves are available in a wide variety of sizes to suit the particular applications. The radiator size not only influences the cooling capacity, but also the oil pressure. When oil flows through a cooler, there is inevitably a pressure loss. This is lower with a narrower, somewhat higher cooler than with a lower, somewhat longer cooler, which is due to the faster oil flow there. As a result, longer, lower coolers are often used to cool transmission or differential oil to speed up oil flow there.
Water-cooled oil coolers (so-called heat exchangers) offer an alternative. In this case, the oil cooler has a tubular design and, in addition to the oil connections, also has water connections via which the cooling water is also routed through the oil cooler, thereby cooling the engine oil. The major advantage of this somewhat more complex design is that the oil cooler no longer has to be placed in the airflow, thus opening up other installation options. The prerequisite for this is, of course, an appropriately dimensioned cooling circuit for the cooling water.
So how does the oil get to the oil cooler? The most common solution for a vehicle with conventional wet sump lubrication is to use a so-called sandwich plate between the engine block and the oil filter. On this plate are the connections for the output to the radiator and the return to the engine. It is important to note that the oil flow in the filter is always from the outside to the inside, i.e. the outer holes receive the oil coming from the engine and the oil is returned to the engine via the center hole (i.e. the threaded hole). Since different vehicle makes have different oil filter threads, the sandwich plates have an interchangeable adapter screw so that installation is possible in almost any vehicle. Such an adapter plate naturally increases the overall height, which can become a problem in some installation situations. Alternatively, it is therefore also possible to install the oil filter offset from the original location and then route the oil from there to the oil cooler. If the oil cooler is installed in a road vehicle, it is recommended to use a thermostat, whereby the circuit to the oil cooler opens only at a temperature of approx. 80°C.
And then, of course, it is necessary to connect the individual components with each other. For road applications, people like to use inexpensive rubber hoses that are secured with hose clamps. For motorsport use, however, it is advisable in any case to choose stainless steel-coated hoses with fittings that comply with aviation standards. After all, the loads here are significantly higher! And then there are often various accessories, such as temperature or pressure displays. For this, the sensors must first be positioned, and it is essential to bear in mind that a temperature sensor must be located directly in the oil flow for a correct display. Staggered installation is only possible with pressure sensors. For both, there is a wide range of corresponding adapter pieces and sensor receptacles that can be integrated directly into the power system. And – last but not least – the oil quality used naturally also plays a role in all these considerations that should not be underestimated!
As you can see, the installation of an oil cooler often makes sense, but there are many options and possibilities. Our team will be happy to advise you at any time.