October 22, 2021


One of the most popular OFH’s (Oil Filter Housings) that a lot of us around the DSM Community use, including myself, is the infamous 1990 externally air cooled 1990 DSM OFH’s. There are a LOT of benefits from using the 1990 OFH and I will do my best to touch on all of them in this FAQ.

Text by AJ Hunsinger // Photos by AJ Hunsinger & ExtremePSI

Pro’s of Using the 1990 OFH

  • Less coolant lines- The 90 OFH is an externally air cooled OFH whereas the regular, normal DSM OFH’s are internally water cooled. With no coolant lines running to your OFH, means there won’t be any coolant leaks. Less leaks on our cars is always a good thing.
  • More oil capacity- Because of the additional space in the oil lines and the oil cooler itself, there is a good gain in oil capacity. How much will be determined by the size of the oil cooler you are using as well as the size and length of the lines.
  • More efficient cooling- Many people say that the air cooled oil cooler is a better way to lower your oil temps. With the water cooled coolers, the hot or warm water in your cooling system is what is used to cool the oil cooler. With the air type, cooler air flows through the cooler thus cooling down the oil. Of course the speed you are driving, chance of airflow based on where you mount the cooler, and the temperature outside will drastically make an impact as to how well it cools the oil.
  • It looks badass- At the very least, your car can look more “racecar-like” depending on how visible the oil cooler is once mounted. If you fab up the front bumper so it’s easily visible, it will look amazing, especially with them beautiful SS Braided lines and -AN fittings.

Con’s of Using the 1990 OFH

  • Warm up operation/cold starting- Literally the only negative that I have been able to come up with for using a 90 OFH is that of some less-than-desired situations at start up. When you first start a car, the oil is generally going to be colder if it hasn’t ran in several hours. The oil temperature should be around the same as the outside air temperature. With a coolant type cooler, the coolant warms up rather quickly. On a colder day, it may be more practical to have the coolant cooled OFH as it will help “heat up” the oil considering water will heat up and cool down faster than water. But, any negative effects of this would be minimal and probably even immeasurable.

90 OFH Holes, Fittings, and Ports

This image shows all of the ports, what go to them, and the thread size for each

The 1990 OFH is obviously only available for the 6 bolt engines as all 1990 DSM’s came with a 6 bolt. With that said, the 90 OFH is only able to be used on the 6 bolt engine. But, there are options out there for the 7 bolt guys, aside from a 6 bolt swap, they they too desire using a nice and safe externally air cooled setup.

Image result for "forward facing" ofh dsm 7 bolt
FF (Forward Facing) OFH- The FF OFH’s are also externally air cooled OFH’s and they are found on the Mitsubishi Mighty Max’s and Dodge Ram 50’s. They also came in 6 bolt form as well as 7 bolt form. These can be easily found on one of the many reputable DSM Vendors
Mitsubishi Evo VIII OFH. The Evo engines are also 7 bolt engines and these OFH’s can be used on the 2G 7 bolts. Just use the 2G OFH gasket