Q: What kind of gear oil do you recommend?

A: For our DSM and 3S transmission rebuilds we recommend factory Mitsubishi 6-speed manual transmission gear oil from the 2005 Mitsubishi EVO MR. (Part number mz313376). This is the best oil to use as it has the perfect blend of friction modifiers to keep the tranny shifting smoothly and prevent gear failure. Please make sure you use the proper amount as specified in your owners manual (typically 2.4 Qts.) Gear oil choice is very important and varies based on preloads and synchro blocker ring design, therefore it is strongly recommended that you stick with this fluid for our transmissions. If you are unable to locate Mitsubishi MR 6-speed oil from the Mitsubishi dealer, Redline Heavyweight Shockproof 50/50 mixed with Valvoline 80W-90 gear oil will also work just as well. For transfer cases and rear ends, use Redline Heavyweight Shockproof ONLY. It is especially important to use only Redline Heavyweight Shockproof fluid or Mitsubishi dealer t-case fluid in EVO transfer cases. DO NOT use Synchromesh, BG Synchroshift I or II, or Royal Purple. These fluids will destroy synchros and gears and void your warranty! THESE ARE THE ONLY FLUIDS WE HAVE EXPERIENCE WITH. If you ask us "Will xyz fluid be okay?" we won't have an answer for you.

GL-4 Gear Oils

We strongly recommend using a GL-4 spec transmission oil in the Mitsubishi manual transmissions. This oil offers good protection for the gears and bearings against wear out. Do not use any oil that has a GL-5 rating in the transmission, for these oils will not give the best shift quality because the GL-5 rating might end up being too slippery for the synchronizers to be effective for high rpm shifts.

There are several GL-4 gear oils on the market for you to choose from. Redline MTL is excellent for daily drivers & weekend warriors and those who live in cold climates while Redline MT-90 is recommended for road racing type service. Both of these oils have proven themselves as a worthy oil for those who want to shift fast, yet are also looking for long service life from their transmission. There are concerns about using Redline's Shockproof type gear oils inside manual transmissions. While this is truly an excellent product, it has been found that the heavy paraffin-like particles are quickly centrifuged out of the oil and build up inside the center diff housing and around the synchronizers and inside of the gearshafts. After several oil changes this build up may block oiling passages inside the gearshafts that lubricate the needle bearings and can reduce the overall effectiveness of the synchronizers, leading to poor shift quality. Therefore we do not suggest using Shockproof in the transmission unless the transmission is to be serviced often or a dog box.

Another transmission oil that works very well is Diaqueen Super Multi part # MZ313376 and it available at the Mitsubishi dealer. Mitsubishi strictly specifies this oil for the EVO-MR 6 speed transmission but it can be used in the 5 speeds, it works and we recommend that you use it if you can't find Redline MTL or MT-90.


Synchromesh/Synchroshift gear oils

While it has been found that the Synchromesh/Synchroshift type oils can sometimes improve the effectiveness of the synchronizers, allowing for faster shifts at higher rpms, this oil does not have enough film strength to ensure the longest gear and bearing for the Mitsubishi transmissions that lives behind a high torque engine. Synchromesh/shift type oils are used in transmissions that are found in low torque applications that don't ask much from the oil in regards of film strength. If you have a weak synchro, you may want to try the “Synchromesh /shift” type oils. However, it is our recommendation that you use the proper GL rating that the transmission was designed to use. Check your owner's manual for this information.

What gear oil should I use?

There are several gear oils that will work depending on horsepower or intended use. For most transmissions we recommend Redline MT90 or Pennzoil Synchromesh. For drag use or high horsepower cars please contact us. Please let us know if you need any Redline gear oil.