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Old 04-29-2004, 10:11 PM   #1
DrD
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Default Thoughts on gear oil... and Subaru's response

So this is interesting:

I asked this question of Subaru:

Quote:
I have a question regarding gear oil used in the manual transmission of a WRX (02) - in the manual it specifies a GL-5, but GL-5's are notoriously bad for synchro's (sulfur based additives are corrosive) - is it acceptable to run a synthetic GL-4 rated gear oil, such as RedLine MT90 or Penzoil Synchromesh in the manual transmission, or would this cause problems? (these oils have a history of significantly improving the performance of synchro-based manual transmissions). A synthetic should be more resistant to shear thinning than a conventional, so I would think that the GL-4 rated synthetic would outperform a conventional GL-5 in some respects. There are also GL-5 rated synthetics which are supposed to work well (such as Motul Gear 300 or Royal Purple Maxgear) - but these don't have the same reputation (and I don't have much experience with them)
This is what I got as an answer:

Quote:
Thank you for visiting the Subaru Web site and for your inquiries.

First, we do not recommend synthetic products for our vehicles, except for synthetic engine oil. We have not tested other synthetic products in our vehicles and do not know how they will affect it. We have tested synthetic engine oil, so there is no problem with using that product. It is not that there will definitely be a problem with using synthetic manual gear lube. It is just that we do not know if it will or not and therefore cannot recommend it. If a problem were to arise, your warranties would not cover the repairs, since you did not follow our recommendations. We recommend that you adhere to the information/recommendations detailed in your owner's manual and/or 'Warranty and Maintenance' booklet.

Again, we do not know if using these products will cause a problem with your 2002 WRX, but, we also cannot recommend or state that it will not cause a problem.

Thanks for the opportunity to be of assistance. If you need any future assistance, please feel free to contact us again.

Best Wishes,

Natalie Cox
Subaru of America, Inc.
Customer Dealer Services
Based upon their response, it sort of sounds like any synthetic will void the warranty on the transmission... however, they also say you can't deviate from what is spelled out in the manual - but the manual only states that the oil must be an API GL-5 rated oil - it says absolutely nothing about synthetic vs. conventional....

I am still curious about the MTL/MT90 thing - both of those RedLine oils work really well in synchro based transmissions - and from the product info sheet on the RedLine website, they say:

Quote:
MTL® can be used in most manual transmissions and transaxles for both street and racing use unless the manufacturer requires the additional protection of an SAE 90 or the extreme-pressure protection of a GL-5. In those situations the MT 90 (GL-4) or 75W90NS (GL-5) will provide good shiftability and synchro compatibility and extra gear protection.
I did send the followup question (below) and I am waiting to hear back...
Quote:
I just wanted some clarification - in your note you state categorically that synthetic gear oil is not to be used in Subaru transmissions, and that we need to adhere to the guidelines defined in the warranty and maintenance book. The only thing specified in that book is that an API GL-5 rated lubricant be used - there are a large number of GL-5 rated synthetics designed for synchro based transmissions(Motul Gear 300, Royal Purple Maxgear, Redline 75W90NS, etc.) - are you stating that those violate the guidelines? I don't see how they could, as they meet the single specification which you guys put forth - that the oil be GL-5 rated.

I would assume that the GL-4 rated oils (Redline MTL/MT90, Penzoil Synchromesh, etc.) would be inappropriate - I was just curious since the synthetics are far more resistant to the degradation modes of gear oil (i.e., shear thinning, contamination, etc.) if a product which met the GL-4 spec would work (since the oils which I mention are well known to dramatically improve the performance of synchronizer based manual transmissions)

Are all synthetics, regardless of whether or not they meet the specifications provided in the warranty and maintenance book, inappropriate and thus violate the vehicle warranty?
I am reasonably sure the person is sending a canned response... I am sort of curious what the real answer is.

The GL-5 requirement seems like it would be overkill for the transmission - it's probably driven more by the center differential than anything else... so that makes me question the use of the RedLine MTL or MT90... they don't recommend using MTL or MT90 in a differential...
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Last edited by DrD; 04-29-2004 at 10:31 PM.
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Old 04-29-2004, 11:23 PM   #2
Mike Wevrick
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Default

IIRC the GL-5 requirement is because of the diff, not the tranny. I agree with you about the synthetic/warranty issue. The manual doesn't say not to use synthetic tranny oil so how can they deny warranty coverage if you do?
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Old 04-30-2004, 02:13 AM   #3
Gunner
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I sent a similar question before and another NASIOC'er sent one, and the answer is the same as this one. ie doesn't recommend synthetic gear oil, but synthetic engine oil is ok.

From that email, it doesn't sound like they can/will void your transmission warranty if you use GL-5 synthetic gear oil with the correct viscosity. But it sure does if you use GL-4 or synchromesh (which isn't classified as GL-4, unlike what you say). Of course, you "may" get good results from out of spec fluid like GL-4 and synchromesh, if you are willing to take the risk.
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Old 04-30-2004, 06:46 AM   #4
Barry
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I have used a blend of 2.7qts Agip (dealer) gear lube with a qt. of MT 90 for almost 20k miles with absolutely no problem.........main benefit is smooth shifting regardless of temperature.........and it was very cold this winter on the Island.
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Old 04-30-2004, 07:17 AM   #5
DrD
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Quote:
Originally posted by Gunner
But it sure does if you use GL-4 or synchromesh (which isn't classified as GL-4, unlike what you say).
sorry 'bout that - I do know it's classified as a GLS, but they recommend it for some transmissions which require a GL-4, so I figured it was reasonably close to a GL4
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Old 04-30-2004, 08:55 AM   #6
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SoA will probably never recommend a synthetic gear oil because of the different results that people get. IMHO, a lot of it has to do with individual driving style. No synchros in the engine so they don't have to worry about anyone messing that up by slam shifting.

I've used synthetic gear oil for the past five years or so, and it's never been an issue. Of course they wouldn't recommend a GL4 since the manual specifies GL5, regardless of how many people have had success with it.

-Dennis
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Old 04-30-2004, 10:38 AM   #7
Gunner
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DrD, do you have shifting problems? Why don't you give the dino GL-5 (like the Valvoline 75w-90 dino) a try before trying GL-4 / synchromesh. So far, people here seem to have good results from it.

And don't worry about it corroding the bronze synchros. MT-1 is the spec that test for yellow metal compatibility. And the Valvoline dino is GL-5 and MT-1 certified.
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Old 04-30-2004, 10:43 AM   #8
heffergm
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I don't care what someone from SOA says in regards to gear oil voiding or not voiding my warranty.

The bottom line is that my manual specifies a GL5 rated gear oil for the transmission... nothing more, nothing less. They can recommend whatever they want, but unless they specify in the manual that I should or should not be using synthetic, then it remains up to me to do so. Provided I pick a synthetic oil that meets all their requirements (which I have), they have no choice but to honor any warranty claims that may come about.

For what it's worth though, I've never had a problem with my transmission, other than it being a bit of a bear when cold. I switched a few hundred miles ago to Amsoil AGR GL5 synthetic, and I'm plenty happy. A little better in the cold, and the same as dino otherwise.
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Old 04-30-2004, 11:04 AM   #9
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DrD - thanks for the info. Quick question - what is the proper email address for technical questions such as these?

Thanks,

-st
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Old 04-30-2004, 04:37 PM   #10
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Ok - so here's the follow up response I got from Subaru:
Quote:
Thanks for taking the time to clarify our response. As we have not tested synthetic (GL-5) transmission or gear oil, we cannot recommend that you use it in your vehicle. We have tested synthetic engine oil, therefore, if preferred by the owner, it can be used in our vehicles. We are not stating that other synthetic fluids would cause a problem in a Subaru; but, as we have not tested, we can also not state that it won't cause a problem.
Therefore, our recommendation is to not use it.

If a product that is not recommended cause a problem with your vehicle, you would be responsible for the repairs. But, in all honesty, using synthetic automatic or gear oil should not cause a problem. Ultimately, you will need
to make this decision.

Thanks for the opportunity to be of assistance. If you need any future assistance, please feel free to contact us.

Best wishes,

John J. Mergen
Subaru of America, Inc.
I still don't understand how they can state that a synthetic GL-5 doesn't conform to their recommendations, which call for "API classification GL-5" - they don't say anything about synthetic vs. conventional in any of their documents... I'll follow up again and see if I can pin them down...
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Old 04-30-2004, 05:06 PM   #11
Gunner
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Gee... just let it be. They say they have not tested it, so they cannot recommend it. It's clear enough. If you like synthetic, just go with any synthetic GL-5 you like. It fulfills the requirement already. If a SOA rep who's job is to reply to emails, tell you that you can use canola oil in it and won't void your warranty. And you use it and the car blows up, do you think SOA will warranty the car? Just go with whatever is specified in the manual. Life has enough headaches already. Just my $0.02.

Before you go with synthetic, search the numerous gear oil threads on something like "oh it feels great I just switched to synthetic" and those "after 10k miles with synthetic I have developed a grind and I am switching back to dino" threads.

It is better time spent than chasing that rep.
Quote:
Originally posted by DrD
Ok - so here's the follow up response I got from Subaru:


I still don't understand how they can state that a synthetic GL-5 doesn't conform to their recommendations, which call for "API classification GL-5" - they don't say anything about synthetic vs. conventional in any of their documents... I'll follow up again and see if I can pin them down...
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Old 04-30-2004, 05:14 PM   #12
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Who cares what SOA says!! Its not like the warranty our trannys anway
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Old 04-30-2004, 06:32 PM   #13
DrD
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Quote:
Originally posted by Gunner
They say they have not tested it, so they cannot recommend it. It's clear enough. If you like synthetic, just go with any synthetic GL-5 you like. It fulfills the requirement already.
I already made the choice a while back - I have been running Motul Gear 300 for a little over a year now with no problems whatsoever. (other than the slow 2-1 transition - but that was there before I changed)

I am concerned because, true or not, there is a perception here that getting Subaru to warranty legitimate transmission issues can be difficult or impossible in cases - it concerns me when they are saying something doesn't meet their recommendations when it clearly does.
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Old 04-30-2004, 09:54 PM   #14
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level round' here...

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not another tranny fluid thread

Its cool that you contacted SOA for there opnions, but I still feel like we are kicking a dead dog. IIRC ppl have already done this many times before with the same results it doesnt seem like a new idea to me.
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Old 05-01-2004, 01:26 AM   #15
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What does it matter, if you're taking it in for repair then put in some dino oil and they'll kiss your behind.
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