Perhaps a better 6MT Fluid

As pretty much every 6MT 5th Gen owner knows, that our transmission are notchy and if you drive the factory filled fluid in the winter, getting into 1st or 2nd gear is initially ridiculously hard on the coldest days. Using the Motul300 improves the shift feel and helps with the cold weather shifts, but it is still hard to shift into 1st or 2nd gear on the coldest days. My friend describes my shifter feeling like its a metal rod in a buck gravel, which is really isn't all that far off.

 

I was reading NASOIC and stumbled upon that new 2015 WRX use the Subaru Extra MT as the factory fill for the 6MT, which I read that it is a 75w80 fluid. Supposedly if you replace the factory fill in the newer WRX for the Motul300 that it results in notchier shifts and initial stiff cold weather shifts. I know the WRX transmissions are based on our transmissions. I did not look to see what the current gen Forester 6MT are using for fluid which are also using a transmission similar to ours. Did Subaru develop a fluid to improve the shift of our style transmission and improve the cold weather gear shift?

 

The one downside of the Extra-MT is Subaru only sells it in 5 gallon pails. List is $420, but on top of that its 150k miles of fluid changes if one changes their fluid every 30k miles.

There are sellers on amazon that sell extra s by the quart. That's where I bought mine. It's better than what was in it.

 

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There are sellers on amazon that sell extra s by the quart. That's where I bought mine. It's better than what was in it.

 

Sent from my SAMSUNG-SM-G920A using Tapatalk

 

Extra MT is different than the synthetic Extra S

From what I've read, the old Extra S is no more, and it was replaced by the new Extra MT (which I thought was an 80W-90 oil). I remember seeing that some vendors were selling the new formula under the same name, which caused a few people some heartburn.

I will say it again, BG synchroshift is the best in our trans by far. I've said it before and people got all twisted about weights and bs. BG makes awesome products and stands behind them. I've ran 6 different fluids in mine and nothing has been as good. Please just try it.

It's still only a GL-4 rated gear oil. There are a number of great gear oils for synchronized manuals - I used to use Redline MT90/MTL in previous cars and it made a big difference. Others seem to like Penzoil synchromesh (don't think that's even rated GL-4)

 

Subaru requires a GL-5 - can you get away with a good GL4? perhaps. But until they make a product like Redline MT90 or Penzoil Synchromesh or whatever that meets that extreme pressure spec, it's Motul Gear 300 for me.

I did a little more research. On the 5 gallon pail Subaru Extra MT is labeled as a 75w80 oil. I found that the 2014 service manual Legacy 6MT lists Extra MT as the recommended fluid (it does not list the weight), the other recommendations are for GL-5 75w90, so Subaru does actually recommend Extra MT for our generation MT transmission. The BG Synchro shift is GL-4 75w80 so technically Subaru does not recommend that fluid.

 

The service manual I saw for 2013 Legacy calls for GL-5, 75w90, so the change probably corresponds to when Extra MT was available. I tried looking at part numbers for 2012 transmission, but apparently Subaru made a few change for 2013 & 2014. Their could be some slightly differences due the FB25 change over as well, because the case part number changed as well. That being said Subaru lists different part numbers for the 2011 and 2012 6MT as well.

Very interesting... So what is the suggested gear oil for a 2012 6MT 2.5i Legacy? I am using Extra MT. Would Motul Gear 300 be a better oil? Gear protection, longevity, and smoother shifting in cold weather are my goals. Or is there really no definitive answer?

 

Thanks.

Byll

Hopeful bump for an answer to my post, above. I need to change my gear oil... Thanks, in advance.

For 2012, it states in the service manual that its 75w90 GL-5 Fluid, so that is the safe bet.

 

You could contact Subaru to see what their take is on using the 75W80 Extra MT and to see if the recommendation for 2014 applies to the 2012 6MT. I would go a little further than just asking the service department unless Subaru released some tech notes for using it. I suspect that its fine and this was the Subaru's solution to our transmission driving and cold weather characteristics, but I am not going to warranty anyones transmission for failure either.

 

This is from the WRX documentation. I found the footnote #4 about the driveability and fuel efficiency interesting.

 

http://i.imgur.com/ADVTFvM.jpg

^^^ good read thanks for the info.

I would probably give the Extra MT a try in a 2.5i, but not necessarily a GT where there's more torque to protect the gears from.

I have had my 2011 LGT for only about a month now. 90k mi. I see from service records the front and rear diff fluids were changed out once (so the tranny as well). I believe they used BG 80w90 in both.

 

When I got the car I was fighting with the notchy shifter. I changed the fluid out about a week later with Motul 300 (75w90). I haven't noticed an improvement. When I say it's notchy its not just getting used to the feel of a new car. For instance if I get stuck in stop and go traffic, I find it hard to get back into first or second even at a slight roll. If I double-clutch it with a mild rev, I find a much easier engagement. Sometimes 2 to 3 will not go smoothly without a blip of throttle. So it's not just notchy, it's conditional... if I get it closer to synced then it slips in easy.

 

I have already ruled out any clutch issues. Damper removed and extra bled, I have at least 1 or 1.5 inches from the floor until the clutch grabs.

 

Is the Motul oil pure gold, or is it just a little too slippery for the syncros?

I have had my 2011 LGT for only about a month now. 90k mi. I see from service records the front and rear diff fluids were changed out once (so the tranny as well). I believe they used BG 80w90 in both.

 

When I got the car I was fighting with the notchy shifter. I changed the fluid out about a week later with Motul 300 (75w90). I haven't noticed an improvement. When I say it's notchy its not just getting used to the feel of a new car. For instance if I get stuck in stop and go traffic, I find it hard to get back into first or second even at a slight roll. If I double-clutch it with a mild rev, I find a much easier engagement. Sometimes 2 to 3 will not go smoothly without a blip of throttle. So it's not just notchy, it's conditional... if I get it closer to synced then it slips in easy.

 

Once the transmission is warmed up, I don't have any issues downshift 1st or 2nd gear or 2-3 upshift. I have experienced other MT issue where the prior owner damaged the synchro's from missing WOT shifts or excessive downshifts into 1st and 2nd at the top of the gear ranges. I wonder if the prior owner of your car was rough on the snchro's. By double clutch and revving you are basically eliminating the synchronizers by matching the shaft speed that you are going into.

The Motul gear oil isn't going to fix a synchro issue, if indeed that's what you have. The LGT transmission is a bit notchy/rough, but I don't have any issues doing 1-2, 2-3, 3-2, or 2-1 (or any others, for that matter) and I've been running Motul Gear 300 since I had 15k miles on the car. The not being able to downshift if you are even at a slight roll sounds like a synchro issue... maybe try one switching out a quart with something that's supposed to improve synchro function (maybe synchromesh, or one of the redline oils (MT90 or even lightweight shockproof) if it's really bad.

Let the car run for a few minutes before you drive off. It doesnt matter what type of fluid you use, it's still 75 weight oil. It needs to warm up a little bit to properly lubricate. Turn key and go is a bad habit that can have negative effects long term.

So far I've had:

 

1. Factory fill

2. Extra S

3. Mag1

4. Extra S (Current)

 

Had a stockpile of Extra S from before they discontinued it so that's why back as the current fill. It's odd the Mag1 fluid despite being the correct viscosity and rating did not work out as well as the Extra S. Cold shifting was rather miserable in comparison. I suppose not all fluids are engineered equally.

I think you're missing the fact that this is in effect an oldskool 5MT with one more gear pair crammed in. Scotty's Cocktail fixes most synchro issues on the 5MT. It certainly did on mine. Try that.

Damn that is a shame. With the STI 6 speed I do not need to worry about trans fluid anymore.

 

Edit: Providing it works of course

The Motul gear oil isn't going to fix a synchro issue, if indeed that's what you have. The LGT transmission is a bit notchy/rough, but I don't have any issues doing 1-2, 2-3, 3-2, or 2-1 (or any others, for that matter) and I've been running Motul Gear 300 since I had 15k miles on the car. The not being able to downshift if you are even at a slight roll sounds like a synchro issue... maybe try one switching out a quart with something that's supposed to improve synchro function (maybe synchromesh, or one of the redline oils (MT90 or even lightweight shockproof) if it's really bad.

 

I don't think the syncros are trashed, but they may have seen some abuse. I am really sensitive (picky) about the effort required to get into gear. I haven't had any grind but I don't push too hard without reverting to a throttle blip or double-clutch.

 

I was thinking of trying a quart of synchromesh or but I am hesitant to try a cocktail after seeing some of the UOAs. Would love to try real Extra-S but that's going to be hard to find.

 

I don't want to lose the front diff protection either. I have only about 1k on the Motul... Maybe I give it a bit longer?

 

Also just got my Perrin shifter bushing and stop. Gotta get those installed!

Get that bushing installed ASAP. It will get rid of the squishy stock bushing and give you a more direct feel.

Reviving this for an update. I have swapped out 1qt of the Motul with 1qt RedLine Lightweight Shockproof. After about 300 mi of daily driving I feel it has made a significant improvement in effort to shift at most all speeds and temperatures. I can only assume that the shockproof provides slightly more friction at the syncros.

 

I may consider going 50/50 at the next fluid change (a la Andrew's cocktail), but I'm happy with the current mix for now. Plus I put the slightly used motul in the rear diff so no waste!

I saw the other 6MT fluid flush thread last night and remembered that the prior owner had used "uncle's scotty cocktail" on GT about 5k miles ago. I had heard of this cocktail before, but never looked into it. I did some research and was a little surprised to see some bad oil sample and some issue on NASOIC I didn't find the thread, but someone mention that even uncle scotty doesn't even use the uncle Scotty's cocktail any more.

 

I am going to make the investment and buy a 5 gallon pail of the Extra MT to try out. 5 gallons is about 150k miles of transmission fluid, which is more miles than I will likely get out my GT, but I am planning to buy a WRX.

Perrin shifter bushing, it should be in the sticky's.

I used the extra S and it needs warm up time for sure even down here. I will need to change it maybe around the first of the year, its been a while. I will probably use motul or extra MT depending on reviews.