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The FSM calls for GL-5 gear oil for the manual transmission on this car.  So I should be fine with any conventional gear oil that has the GL-5 rating on the can?  I plan to go with 75W-90 as far as viscosity rating goes.

 

Thanks.

 

Mike V.

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I beleive people like castrol synthetic 75w-90 gl-4 gear oil. I'm thinking about trying out mobile 1s equivalent to this I'm my car its about $15 a quart though

Edit: to be clear I am using a gl-5 gear oil. Mobil one 75w-90 LS synthetic

Edited by mikaleda
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That thread offers a variety of opinions.  I guess it is like any motor oil thread - lots of widely differing opinions with no clear consensus.  At this point I will probably go ahead with a conventional, name  brand GL-5 oil and see how it shifts. 

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I beleive people like castrol synthetic 75w-90 gl-4 gear oil. I'm thinking about trying out mobile 1s equivalent to this I'm my car its about $15 a quart though

 

Don't use anything besides GL-5 gearoil with a hypoid differential, like the one inside the transmission. 

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Don't use anything besides GL-5 gearoil with a hypoid differential, like the one inside the transmission.

It is gl-5 I missed typed. Here is the description from amazon

Description

Mobil 1 Synthetic Gear Lube LS 75W-90 Mobil 1 Synthetic Gear Lube LS 75W-90 is a supreme performance, synthetic, multi-purpose, SAE 75W-90 automotive gear lubricant designed to meet the highest level of performance requirements of modern passenger vehicles in all types of operating conditions, including limited slip applications, as well as delivering outstanding power transfer performance. Compared to conventional hypoid gear lubricants, Mobil 1 Synthetic Gear Lube LS 75W-90 performs exceptionally well over a wide range of temperatures. It achieves this through a unique proprietary formulation that delivers optimized viscosity as a function of temperature properties together with the highest level of inherent formulation stability and protects against thermal and oxidative degradation, wear and corrosion, and viscosity loss associated with premature shearing. It also can be used in extended service and for aiding in fuel economy performance. It contains special friction modifiers designed for limited slip-type differentials. In most applications, the addition of special LS (limited slip) additives is not required. For axles requiring the highest level of limited-slip performance, OEM specific LS additives can be added to this fluid. It combines wax-free synthesized hydrocarbon base oils and a specially designed extreme-pressure, limited-slip, sulfur-phosphorous additive system to provide a significantly higher level of performance in rear axles and differentials versus conventional fluids. Greater film strength at higher operating temperatures, reduced fluid friction and low-temperature application down to -50 degree celsius provides significant advantages versus conventional mineral oil formulations. It reduces wear and spalling under the high speed, high torque and high horsepower conditions in competitive racing and high performance automobiles.

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fine for the rear diff, but some people report problems with using synthetic in the trans. If you do to, switch to a non-synthetic and see if it gets better. The synchros spin too fast with synth. Even Subaru's Extra-S isn't synthetic.

 

huge thread at http://forums.nasioc.com/forums/showthread.php?t=920674  you could search thru it for people reporting results using Mobil 1, Redline, Royal Purple or w'ever lube you can think of.

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The reason I was thinking of moving to synthetic is because of the very cold winters we get up here. Its very hard in my transmission when its -10 and even after warming up the engine having to push my way through a couple feet of fresh ssnow. I want something that won't turn to mallases when it gets cold. Also since the product uI am looking at has a friction modifier in it already I don't think it should have any problems with the syncros. They do operate very similar to a LSD diff anyway. I already am having issues with reverse and first engaging. I generly rpm shift anyway so I don't think abeing to slippery for my syrncros will be an issue.

Edited by mikaleda
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Looks like since part of that process is adding a friction modifier the oil I'm looking at shouldn't need that Parr of the cocktail. I might add a quart of the redline heavyweight additive they talk about in the post I can see how that would help keep the gears coated in oil.

 

Myain concern has always been the input shaft bearing, I was thinking the most likely reason for failure is the warm up period when the trans is cold and not getting any lubrication from the conventional 80w-90 and that is part of the reason I wanted a thinner oil.

I think I'll try mobile one with a quart of redline heavyweight to help the syncros

 

Okay I just ordered a cocktail of redline heavyweight shock proof and 3 quarts of mobile one synthetic LS I'll post my results and let you guys know how it works.

Edited by mikaleda
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Don't use any of the random mixes of different oil in your transmission. There are huge threads on NASIOC about it, and the result is a lot of ruined transmissions. If you want the very best oil for the transmission, get subaru extra-S and be done with it. Or use a good quality GL5 gearoil and it'll also be fine. A lot of additives to different oils are bad for soft metals used in synchros, there's one way to find out... I live in Maine and it's also freezing cold in the winter, I ran napa premium GL5 gear oil in all my manuals and never had a problem.

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Don't use any of the random mixes of different oil in your transmission. There are huge threads on NASIOC about it, and the result is a lot of ruined transmissions. If you want the very best oil for the transmission, get subaru extra-S and be done with it. Or use a good quality GL5 gearoil and it'll also be fine. A lot of additives to different oils are bad for soft metals used in synchros, there's one way to find out... I live in Maine and it's also freezing cold in the winter, I ran napa premium GL5 gear oil in all my manuals and never had a problem.

I agree I don't like mixing a bunch of different oils, I am going to try straight mobile 1 and if I don't like it I have a quart of redline I'll add.

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If you live in a cold climate use Motul 300.

I just put it in the trans in my 96 which was a nightmare to shift in the cold running standard 80-90 gl5. Put the Motul in and the difference was immediate. Shifts smooth as silk every time. Well worth the $80. Wish I had made the switch a year ago because it would have saved me a lot of headache last winter when I put that trans in the car.

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I swear this subject is so freaking varried its hard to tell what is a good idea and what's not. Every single thread I've read is like this. One person suggests a brand of oil, the next says it won't work. Then someone says mix this and this and then you have the right oil :headbang: (I agree I don't like the idea of mixing oils) and the next person says no that will ruin your transmission.

 

The thing is these transmissions are known not the be very long lasting so there is no way to know if the reasons people have a failed transmission is because of the oil they put in it or if it was already on its last legs and nothing was going to save it.

 

I have to change my transmission fluid anyway so I'm going with the extra-s since its the only one that says its made for subaru. Its a 75w-90 so maybe it will be better cold shifting (I hope) if not I'll change it next year and try one brand of synthetic and see what happens and if its like some people say I'll try adding a quart of a oil stabalizer and see what happens. Since I have a few of these transmissions around and a couple of stick shift cars, I should be able to try it out on a couple of cars at the same time and find out for myself. Once I figure it out I'll post my results so no one else has the headache I have now.

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I have to change my transmission fluid anyway so I'm going with the extra-s since its the only one that says its made for subaru.

This is what I was going to do. Then I found out the real Extra-S is no longer available in the US. The new stuff currently marketed as extra-s is not the same stuff, and several people who have used both have reported a downgrade in shift quality after switching to the new stuff.

It took me a LONG time searching to find info on which out of all the gear oils people use would suit my needs. I finally decided on the Motul 300 because of several posts I read from a shop owner in New Jersey. If it works in the NJ cold, it'll work in central VA.

 

I put the stuff in back in late summer when highs were still in the 90s. We've had a few mornings with temps in the low 30s so far this fall. The trans shifts exactly the same, hot or cold.

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yeah, now that Extra-S is in liter bottles - hard to say no to it. If it seems to cause problems, then maybe investigate something else.

 

The Motul 300 suggestion I think is good too. It seems to have a lot of fans.

 

I do NOT feel scotty's cocktail is harmful to a transmission (someone posted over there recently that the inside of a trans running it looked pristine) BUT, remember that scotty is in Houston. So, I think it is wise to question how it might perform in extreme cold. Many people expect his cocktail to repair a broken trans and when they subsequently crater their trans, they blame the fluid. The idea with it is to help with some synchro clashing. It can't repair something broken or abused. No fluid can.

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This is what I was going to do. Then I found out the real Extra-S is no longer available in the US. The new stuff currently marketed as extra-s is not the same stuff, and several people who have used both have reported a downgrade in shift quality after switching to the new stuff.

It took me a LONG time searching to find info on which out of all the gear oils people use would suit my needs. I finally decided on the Motul 300 because of several posts I read from a shop owner in New Jersey. If it works in the NJ cold, it'll work in central VA.

 

I put the stuff in back in late summer when highs were still in the 90s. We've had a few mornings with temps in the low 30s so far this fall. The trans shifts exactly the same, hot or cold.

i have read the same things about the new extra -s and i still decided i would try it just because i haven't seen a single oil that someone didn't like. I will check into the motul  300 and see what it says maybe ill try that as a next step if im not satisfied with the extra s i ordered. 

wow seems people really like the motul 300 of course its twice the price of extra s or the mobil 1 i was looking at, but it would be worth it if it works like it says it would be worth every penny. looks like the reviews online are quite positive as well. shoot i guess ill order 4 quarts of that oil as well. Ill try the extra s in my outback and ill try the motul 300 in my legacy and see what happens. 

well there goes $140 in oil :rolleyes: 

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Like I said, there are too many conflicting, yet emphatic, recommendations for me.  So I plan on going with GL-5 dino oil,  Actually, I was about to pick up some Valvoline last night at the AutoZone but the label said meets GL-4/GL-5 standards but it also said it was for use in NON-synchro transmissions!  How many non-synchro passenger car gear boxes are made anymore?  Even my 1950's sports cars were all synchro except for first gear for Pete's sake.

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  • 4 weeks later...

I thought I'd post my findings on the three types of oil I tried

 

1.) Conventional gear oil

2.) subarus extra s replacement HDGO

3.) Motul 300

 

All cold weather shifting comoarisons

1.) Feels like molasses and takes forever to get warm enough to shift properly.

 

2.) Better than conventional oil, but is not great cold shifting

 

3.) Great, even in the coldest mornings cold shifts are great and all around performance increased. RPM shifting with the conventional oil was almost impossible, but now is easy and very comfortable. Low end performance is better IMHO. I feel that this oil will actually help increase the life of my transmission.

 

A word of warning motul 300 is sold by the liter and I almost over filled my trans mission thinking they were quarts.

 

In my opinion, subarus extra s replacement is okay, much better than conventional oil, but doesn't hold a flame to the motul.

 

I will be running motul in all my Manuel trans subies from now on.

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