It's well known that the N54 and N55 engines run very hot. Turbos that build a lot of heat and a small radiator play into why this engine runs so hot. A quick look at your gauge cluster on your dash after a few minutes of "spirited" driving, you'll notice oil temperatures over 250 degrees. Considering that most cars don't even exceed 230 degrees tells you quite a bit. As oil temperatures get too high, thermal degradation occurs. This is when the oil starts to lose viscosity due to heat and start to break down and becomes more susceptible to "shearing" or oil breakdown. An internal combustion engine like the N54/N55 engine, imparts high shear forces on the motor oil, which is sandwiched between two rotating or sliding forces under load and heat. "Shearing" is when the molecular structure is essentially torn apart by these mechanical shear forces. Lower your operating oil temperature will greatly reduce this. Thus your motor oil is in better shape to protect the bearings in your car's engine, thus improving longevity.
The 135i/335i comes from the factory with a small oil cooler with a core size of 8.75"x4.75"x1" (222mmx121mmx26mm) which comes out to 41 cubic inches of core. The Sports Series Oil Cooler system features a large 11"x8"x2" (280mmx203mmx51mm) oil cooler with a core size of 9"x8"x2" (229mmx203mmx51mm). The Sports Series Oil Cooler comes out to 144 cubic inches of core which is 3.5 times larger than the factory unit each!
The Sports Series Oil Cooler mounts to its own box enclosure. Louvers on the backside of the box enclosure ensures airflow through the oil cooler while protecting the oil cooler from road debris, especially debris kicked up from the front tires. During initial testing, our box enclosure had a big window (open hole) in the back for airflow. However, throughout the race season, it took so much abuse from rocks, tire and other debris kicked up from the front tires that we had to replace the oil coolers on our Time Attack 135i. Thus, instead of a big hole for airflow to flow through, ER used louvers instead to protect the back side of the oil cooler. This effectively solved the issue without any affect on performance. Oil temperatures as well as oil temperature deltas stayed the same.
Type III Hard Anodize Black Finish:
The oil coolers come standard with no finish (silver color). With the Type III Hard Anodized Black Finish, it is very hard to tell there is an aftermarket oil cooler on the car. Another added benefit of the Type III Hard Anodizing is that it makes the oil cooler fins harder and stronger, which makes it less prone to getting bent/damaged from road debris like rocks etc... ER opted for the Type III Hard Anodizing over the Type II color anodizing which is only asthetics for this purpose only (even though it costs considerably more to anodize Type III than Type II). ER started using the Type III Hard Anodized Black finish on their rally car customer's FMICs years ago. Rally cars go through tremendous amounts of abuse and it was quite common to take hits on the intercooler from debris on the course. In fact after 1 event, often a large portion of the intercooler fins would be bent (killing efficiency) and fixing them after each event was quite tedious. After the Type III Hard Anodizing, a big difference was noticed as there was considerably less damage. Even after hits and even accidents, the FMIC could take more abuse than before. Testing has shown no noticeable ill-effect from the Type III Hard Anodizing on performance (regular spray paint etc... has shown ill-effects on performance).