MTX - When to change gear oil?

[GMFan]

Good evening to everyone,

My Mazda6 (in signature) uses a 75w90 gear oil in the manual transmission. Surprisingly, nowhere in the owner's manual does it say anything about servicing the manual transmission. However, the lubricant spec'd for the MTX is API Service GL-4 or GL-5 75w90

My previous car (Saturn SL) with a 5spd manual transmission used ATF fluid rather than a gear oil and I was advised from the Saturn experts that the ATF in the transmission didn't require any service.

From what I have gathered changing my engine oil the transmission has an easily accessible drain plug and a fill plug. The manual says the transmission uses 3 quarts.

A few questions:

1. If there is no recommended service interval how often should I change the gear oil? I assume like any typical oil it will break down and eventually sludge if not properly maintained....although the lack of "heat" shouldn't stress it too much.

2. How does one actually fill the transmission? Do you use a plastic flexible tube with a funnel and simply pour the oil in? Must this done be performed on a lift so the car is flat rather than on jack stands?

3. Would I be wise to use Mazda MTX gear oil or could I use any 75w90 gear oil that meets GL-4 or GL-5? Is GL-5 "better" than GL-4. Some claim the GL-5 is harsh on syncros?

Thanks in advance.

 

[Rand]

It depends on the vehicle. I would research yours perhaps on a mazda specific forum.
as far as the gear oil

unless your transmission contains hypoid gears I would use a GL-4 75w90 type mtf.

more isnt better on some additives that is in gl-4 vs gl-5 gear oil.

You can always do one change relatively early to get the break in wear out.. or not.

usually MT's have a drain and a fill plug setup.
some have a drain plug and dipstick setup.

 

[GMFan]

Originally Posted By: Rand
It depends on the vehicle. I would research yours perhaps on a mazda specific forum.
as far as the gear oil

unless your transmission contains hypoid gears I would use a GL-4 75w90 type mtf.

more isnt better on some additives that is in gl-4 vs gl-5 gear oil.


Thanks rand,

A lot of users on the Mazda6 board like Redline MT-90 and Amsoil. There is some disagreement on whether to use GL-4 vs GL-5. If I recall some members said the GL-5 was hard on the yellow metal syncros. No idea if that is true or not. The "experts" on car forums typically base there recommendations on anecdotal evidence.

 

[dparm]

There are a gazillion dual-rated GL-4/GL-5 fluids.

 

[SLCraig]

I will save you the hassle of deciding and recommend Amsoil MTG 75w90 GL-4. The stuff is the nectar of the gods. Amsoil is always my favorite in transmissions though. (I have used the MTG, it has such a fantastic shift feel)

 

[Bluestream]

Originally Posted By: GMFan

I was advised from the Saturn experts that the ATF in the transmission didn't require any service.

 

[ABerns]

I have also heard the "GL-4 is best" discussion. I have a 93 MX-6, which isn't in the same class as your car age-wise! However, I've had good luck with Redline MT-90, as have many others on mx6.com. I have only changed it twice and I don't remember how many miles before each change. I do believe these fluids will shear, though, which is a major reason to change (even if they don't sludge up and even after you get break-in metals out).

As far as how to fill it, I did as you said - took a hose attached to a funnel and just ran it from the top. Helps to have a second person to pour while you hold the hose in. Really easy job this way. I prefer to have the car as level as I can, since my fill plug is at the front and I want to avoid overfilling. Just put in fluid until it's at the level of the fill plug.

They do have a pump that goes into gear lube to pump it out. It does not fit the MT-90 bottles very well (they don't look like your "standard" gear lube bottles). The funnel method was quicker for me - YMMV.

 

[SXE10]

Can vouch for MT-90, it's brilliant stuff. I'd say Amsoil will be just as good. Maybe flip a coin to chose which one to use

 

[mechtech2]

Originally Posted By: SLCraig
I will save you the hassle of deciding and recommend Amsoil MTG 75w90 GL-4. The stuff is the nectar of the gods. Amsoil is always my favorite in transmissions though. (I have used the MTG, it has such a fantastic shift feel)


Here ya go!
Why screw around?

 

[GMFan]

Well my car has 58K miles on it and I feel it is time to change out the MTX gear oil. I would have liked to change it out earlier but I am very busy so I have decided to do it over the holidays when I have the time off work. I decided to go with 3 quarts of Redline MT-90 75W90 GL-4 for the gear oil.

I found a how-to online and this looks like an easy job. I was unable to find a how-to for the Mazda6 but found one for the Mazda3. Interestingly, the article about the Mazda3 claims that changing out the MTX gear oil also drains the differential as they are in the same case and use the same oil. I am unsure if this is true or not on the Mazda6.

Hopefully everything goes smoothly! I will post back after the job is complete and if my transmission shifts any better compared to whatever Ford/Mazda put in at the factory.

 

[badtlc]

Is this for the Mazda? Are you sure that is the right fluid? Mazda has been spec'ing 75W-80 (Redline MTL) for a few years, not 75W-90. The cold performance (below 40F) will be drastically worse with MT90 if your coming from a thinner fluid.

 

[Greasymechtech]

90 grade is what was originally required.
80 grade came about because of shift complaints, and for newer models for mpg and shiftability.

Since you're in a colder climate, thinner might be a better choice.

MT90 is a great fluid. But, sometimes it takes a few thousand miles to work into the transmission. Redline MT85 & MTL, Amsoil MTG & MTF, and other OE or aftermarket fluids are choices. Stick with GL4.

I change my manual gearboxes every 25k-50k miles, usually every 2-3 years. I also check and top off cold gear fluid level once or twice a year.

 

[GMFan]

Originally Posted By: badtlc
Is this for the Mazda? Are you sure that is the right fluid? Mazda has been spec'ing 75W-80 (Redline MTL) for a few years, not 75W-90. The cold performance (below 40F) will be drastically worse with MT90 if your coming from a thinner fluid.


Right now I have the factory gear oil in there and the manual recommends GL-4 75W90. I have no idea what Mazda put in the transmission at the factory but I have no reason to assume it isn't 75W90. The shifter definitely feels a little more stiff in the winter but I am not having any gear issues. The transmission has been flawless in my experience.

I re-read the manual and it states the transmission takes 3.12 quarts so I got a 4th quart just to be safe. This stuff ain't cheap...

 

[badtlc]

Originally Posted By: GMFan
Originally Posted By: badtlc
Is this for the Mazda? Are you sure that is the right fluid? Mazda has been spec'ing 75W-80 (Redline MTL) for a few years, not 75W-90. The cold performance (below 40F) will be drastically worse with MT90 if your coming from a thinner fluid.


Right now I have the factory gear oil in there and the manual recommends GL-4 75W90. I have no idea what Mazda put in the transmission at the factory but I have no reason to assume it isn't 75W90. The shifter definitely feels a little more stiff in the winter but I am not having any gear issues. The transmission has been flawless in my experience.

I re-read the manual and it states the transmission takes 3.12 quarts so I got a 4th quart just to be safe. This stuff ain't cheap...


It is hard to say. VW specs a 75W-90 and they put in what is essentially a straight 75W which is WAY thinner than 75W-90. I'm sure the fluid you picked will be fine for you but Mazda has no issues running 75W-80 in the same transmission now days. Redline MTL is a very robust MTF that would suit you well, too without going extremely thin. It is a heavy 75W-80.

Either way i'm sure you'll be happy. Good luck.

 

[JHZR2]

I cant recall any OM that states an interval for MTF replacement. Back when I was using Redline in my gearbox, it would start out wonderful and then quickly degrade... So I knew when to change it. Since changing to Amsoil, it is much more consistent.

The GM fluid in my Saab seems to do the same thing as redline - after a while it starts losing shift quality, especially in the cold.

Our VW has been very consistent, so I just replaced it around 40k, which was convenient weather-wise for when we passed 36k.

IMO the first change is more important than subsequent changes.

 

[147_Grain]

Originally Posted By: JHZR2
IMO the first change is more important than subsequent changes.

+1

 

[GMFan]

So I changed out the gear oil. I have learned on a front wheel drive vehicle with a manual transmission that the transmission oil is shared with the front differential so I killed two birds with one stone.

My impressions with the new gear oil are that my expectations were a little too high. It doesn't seem to shift significantly better than with the old gear oil and the notchiness is still there on cold mornings until warm up. The old fluid was slightly brown and there was some filings on the drain plug.

I will probably change it again in 60k miles. I plan to drive this rig into the ground so changing it out will be for peace of mind. Does 60k miles sound reasonable?

 

[badtlc]

Sounds like you should try the MTL instead of the MT90.

Also, in the cold, start it first thing when you get in the car. Then put it in neutral and let out the clutch. This helps throw the fluid around just a bit more and by the time you put on seat belt, undo parking brake, etc. it might be a bit smoother. It works for me but again, I use MTL and not MT90.