When do you need to upgrade to an aftermarket Oil Cooler?

Since 2004 when STI was first made available here in the States, it has come equipped with an oil cooler from the factory.  And for a number of years, the WRX and other turbocharged Subaru's also came with a factory installed oil cooler.

The reason for this is that although it is always important to keep your cars oil at a normal operating temperature, in a turbocharged car that sends oil through the turbo to keep it lubricated and working properly, it can be more difficult to keep your oil at stable temperature.  This is especially the case if you are driving in hot temperatures, you are driving the car hard at the track, or you are making a good deal more power than the car did stock.

Before we take a look at the factory oil cooler, it is worth mentioning that Subaru stopped putting an oil cooler on the WRX in 2008.  It isn't clear the reason for this, but it could be that for completely stock cars that aren't put on the track, the need stabilize oil temperatures was less.  But if you have a turbocharged Subaru that didn't come with a cooler, this might be one of the first things you would want to add to your car to keep it reliable.

It is actually very easy to add a factory oil cooler to these cars, and we have put a kit together with everything that you need for the job.  The biggest component to install is actually a new water pump because you need to be able to send coolant to the oil cooler.

Now the question that you may have here is, if you are sending coolant to "cool" the oil, is the Subaru part really an oil cooler?  The short answer is yes, but a better answer may be to call it a heat exchanger.  The factory part actually has two jobs.  The first it so make sure that oil temps are stable and controlled in hot conditions and under hard driving.  The second is to help bring the oil up to operating temp faster by using the coolant.

The factory oil cooler/heat exchanger is definitely a lot better to have on your engine in hot conditions or hard driving.  But if you are making a lot of power, or your car is spending a lot of time on track, then you may have better overall results with an external oil cooler.

The advantage to moving the job of cooling your oil away from the coolant entirely is first that you radiator and cooling system now just has to cool the engine, not the oil as well (though those are related).  The other key advantage is that if you have a good oil cooler and you can place it where it can get a good flow of air, you will have a much better ability to keep a constant oil temperature under hard driving.

If you are looking for an external oil cooler for a street car, one key thing that you need to have is an adapter plate with a thermostat.  Since the external cooler is so much more efficient at cooling your oil, in the winter or colder temperatures, you may not want to run your oil to the cooler much at all.  If you run an adapter plate without a thermostat, you may have a hard time getting your car up to temperature.

Even for a full race car, having a thermostat can help ensure that your car comes up to temperature more quickly.

The other thing that you want to consider is routing of the lines to the cooler and location of the cooler itself.  Make sure that you can safely route the lines away from any hot exhaust components (or that you can at least properly insulate them), and that you have a good location for the cooler that will get it good air flow.

If you are going to install an external cooler, it would be a really good idea to have an oil pressure gauge installed on our car.  This is a key piece of information to have regardless, and especially if you are tracking your car.  But when installing an aftermarket oil cooler, you want to make sure that you aren't seeing much (if any) pressure drop after putting the cooler on compared to before.

Having consistent oil temperatures is definitely a key to keeping your engine reliable, and hopefully this is a helpful guide so you can pick the best solution for your application.

Thanks for reading and Stay Tuned!

- Jon Cooley