Gear Oils

TRE recommends using the following manual transmission oils listed below for use in your Mitsubishi manual transmissions including the EVO-X manual transmissions. We critically question the validity of Mitsubishi's recommendation of a GL-3 oil specification for the EVO-X manual transmissions as this oil clearly lacks the proper EP additives to keep the center differential spider gears from seizing to the cross shafts and shearing the retaining pins. Listed below are a few of the gear oils on the market for you to choose from.

MOTUL GEAR 300 75W90. This oil has incredible film strength while still allowing for quick shifts making it another wise choice of oil for your high power Mitsubishi transmission. Scott Evans likes this oil and so does TRE. Part# 100118. Note: We are talking about GEAR 300, not Gear 300LS which is a full GL-5 gear oil and has the friction modifiers that are required by limited slip differentials.

REDLINE MT-90 This gear oil offers improved shift quality in most manual transmissions and would be fine for stock power levels. Part# 50304

REDLINE 75w-90NS. This synchro friendly GL-5 rated "no-slip" gear oil provides improved film strength, reducing the scuffing that we commonly see in modified vehicles that that are making more power than stock, while still offering good shift quality. Part# 58304.

REDLINE 75W140 NS GL-5 Gear Oil. This is an excellent gear oil that will keep the gears and bearings from frosting or scuffing in a high torque application. It's one of the best oils that we know when it comes to gear protection in those mission impossible applications but keep in mind that it may be too slippery for the synchros to work effectively at high rpm shifting. Part# 57104.

AMSOIL Manual Transmission & Transaxle Gear Lube 75W-90 (MTG). This API GL-4 rated gear oil has good stability and film strength and would be fine for near "stock power" levels. Part# MTGQT-EA

MITSUBISHI DIAQUEEN SUPER MULTI GEAR OIL. This oil is rated 75w-85 API GL-4 and we recommend that you use it if you can't find the other oils that we recommend. Part# MZ313376.

FRICTION MODIFIERS.  Never add a friction modifier to your transmission gear oil as it will make for poor shift quality. Understand that the friction modifier is an additive that reduces friction and is designed to reduce noise that limited slip differentials can make while making tight turns at low speeds. Do not use it in your transmission.

REDLINE SHOCKPROOF There are concerns about using REDLINE SHOCKPROOF type gear oils inside manual transmissions. While this is truly an excellent product, it has been found that the heavy Teflon-like particles are quickly centrifuged out of the oil and will 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. Also this oil is has too high of a viscosity for winter use. Therefore we cannot recommend using SHOCKPROOF in the transmission unless the transmission is to be serviced often or a dog box.

Remember that proper viscosity is important when it comes to splash type lubrication; certain parts require enough viscosity so that the oil will get thrown far enough in the proper direct to provide lubrication so please check out the viscosity chart and choose an oil for the operation temperatures of your transmission. Ideal transmissions temps should be between 140-200 depending on what you're doing.

OIL LEVEL: Oil must be level with or slowly flow back out of fill/level plug. It would be wise to drive the vehicle a short distance and recheck the oil level and top off as required.  Road racing & drag race applications may add an additional pint of oil to the transmission for added lubrication and cooling.

EVOLUTION OWNERS TAKE NOTE: It is of utmost importance that the transmission oil be checked again after driving the vehicle due to the oiling circuit for the front differential. You must to drive the car a few miles at speeds over 25mph to fill the front differential housing and then top of the transmission oil level. Driving the EVO with the transmission oil level too low will shorten the service life of the 3rd & 4th gear synchros.

CHANGING THE OIL: Vehicles that are being road raced require race car maintenance and all drivetrain oils should be inspected after each race and preferably changed.  New or recently rebuilt transmissions should have the oil changed after the initial first 500 miles and again after 1000 miles, then every 5000 miles. Contact TRE if you have questions about using a cheaper break-in oil.



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 long gear and bearing life for the Mitsubishi transmissions.

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. Transmissions that call for Synchromesh type gear oils are designed with wide gear shaft spacing which greatly reduces the force on the gear teeth and large bearings so that they can use these low film strength oils. The reason behind it is to reduce parasitic frictional losses and to improve shift quality.

If you have a weak synchro, you may want to try the “Synchromesh/Synchroshift” type oils but it is our recommendation that you use the proper GL rating that the transmission was designed to use and prepare for a rebuild.   

Use of GL-5 spec gear oil isn't recommended in your manual transmission except for certain conditions.  The EP (Extreme Pressure) additives found in GL-5 may reduce the effectiveness of your synchronizers making the transmission shift poorly and tarnish them over time. However, it should also be noted that if you are wanting an oil that does provide higher film strength and added protection against gear & bearing wear, you may consider using a GL-5 spec gear oil. Just remember that it will not shift as good at the high rpms and that it will oxidize the synchros over time.

Transmission gears

A short word about transmission gears. Transmission gears are exceptionally strong and generally have a hardness of 58-62HRC. It is because of their hardness that the gears will take quite a while to fully bed-in together before ultimate power handling capabilities can be obtained. The are several reasons for this and they all revolve around the manufacture's ability to hold tolerance on the parts and to what AGMA or DIN that they cared to produce in the first place. In a perfect world, everything is machined right on the money and you have full and proper contact of the gears that are in mesh but I can assure you that production parts are less than perfect. What does this mean?   It means that it will require some drive time to fully bed-in the gears before you go out there and explore the limits of how much power they can handle without failure. Transmission gears can take as many as 8,000 miles to fully wear themselves in, allowing for full & proper contact and the most strength. It is wise to drive any new or recently rebuilt transmission gently so that the gears bed-in before pushing them to their material limits regardless of what people may tell you.


Transmission synchronizers, like brake pads, will require some time for their surfaces to fully bed-in. Do not shift a new or freshly rebuilt transmission fast or at high rpms for this bed-in process requires that you drive the car gently and shift slowly. You want to allow the synchronizers a little extra time to develop their full contact finish which provides the most friction and ultimately the best shift quality. This process takes a few hundred miles of city driving, where you are shifting through the gears often. Rush this process by shifting the hell out of it and your transmission will not shift as well as it could have. I find that my transmissions shift well around 500 miles and feel damn good after 1500 miles. Take your time and read this page.

By design, synchronizers will either block the driver from completing their shift or possibly grind during shifting into any gear, and for that matter, even make shifting into any gear in the first place difficult if the speed of the clutch disc, input shaft & various other components doesn’t match the speed of the gear they are shifting into. It is crucial that your clutch is operating properly, with sufficient release to allow the clutch disc, input shaft & various other components to be “free” from the engine’s rotating speed thus allowing them to slow down and match the speed of the gear you are shifting into. Synchros are not designed or capable of dealing with a clutch that doesn’t have enough release.  If you are having trouble getting into any gears while the car is running or are experiencing blocking or “notchy” shifting; you must check your clutch, making sure that it's properly adjusted or you will cause damage to the synchronizers. It is sole responsibility of the driver and/or installer to make sure that the clutch is properly adjusted so that is has sufficient release to allow the synchros to do their job without the clutch disc dragging on the flywheel/pressure plate assembly.


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