GL-4 vs GL-5 -- and a letter from Mobil

[moribundman]

LETTER TO MOBIL

quote:

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Current Customer:yes
Question:I need technical info regarding the potential long/short term negative effects, if any, of using MT1 GL-5 transmission oil in a manual transmission that specifies a GL-4 oil be used.

Thank you,
-XXXXXX

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MOBIL REPLY

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The GL-5 lubricant has high levels of EP additives which is sulfur and will erode yellow parts found in many transmission such as brass and bronze parts. Therefore Mobil does not recommend our product be used in any transmission using yellow metals under any circumstances.>>

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I remember being told "modern GL-5" lubes did not lead to yellow metal corossion. I've also heard yellow metal corrosion was only an issue at high gear lube temperatures that will not occur in a street-driven car.

I have noticed that Specialty Forumlations offers GL-4 lube. So it's not an obsolete spec?

What's the deal? Is GL-5 safe to use if GL-4 is specified, or isn't it?

[ January 06, 2005, 07:22 PM: Message edited by: moribundman ]

 

[Grossomotto]

But, I thought the bigger issue was the EP additives and friction modifiers reduced the friction for brass (and other) syncros to properly function? It sounds like Mobil is referring to their 75W90 Gear Oil in a manual trans.

 

[sbc350gearhead]

Some gear lubes are GL4 and GL5 rated. Unless it carries a GL4 rating, you can't use a GL5 fluid in a transmission calling for a GL-4 fluid.

 

[moribundman]

Does anybody want me to find my thread from last year, in which I was REPEATEDLY told that "modern GL-5" lubes would NOT cause any yellow metal corrosion. It was pointed out that yellow metal corrosion was only an issue with older GL-5 lubes. I believe MolaKule said so at one point or another, too.

Here is one of the old threads addressing the issue:
http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic;f=16;t=000442#000033


Let me quote from this thread:

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In theory most Transmissions call for GL-4 because theoretically the synchronizers can not tolerate the GL-5. At the time this was discussed we had a former rep (I believe-from Mobil) post a differing opinion:

He indicated that the GL-4 was no longer a valed spec. He also indicated that the additives in GL-5 have been upgraded to the extent that it is fine for brass synchros

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quote:

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In the past, the additives in the gear oil that allowed it to pass the GL-5 test did indeed corrode yellow metals, brass, bronze, etc. Many modern GL-5 gear oils have a different additive package that is not corrosive to these yellow metals

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recently i called mobil about using their mobil1 gl-5 in a gearbox that spec'd gl-4 because of bronze gears. i figured with it being synthetic maybe it didn't contain the same additives that conventional oil does. he looked in his books and talked to the other reps then came back on and told me "i wouldn't use it in there".

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I wish I had time to post all the information on gl4 vers gl5 as many are concerned with copper corrosion in gl5. This is not correct. Gl-5 actually has higher requirements against copper corrosion than the gl-4.

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I almost have quit explaining that modern GL-4 and/or Gl-5 will NOT eat yellow metal (Cu, brass, bronze) - that is a strong myth.

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I know, it does get somewhat fustrating but that's what we're here for, to help explain as most of this info gets started by someone that has no real clue. I can understand that as there just isn't enough info available to help educate about these things.

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I couldn't agree more!

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A GL-4 cannot be rated as a GL-5 also. A GL-4 has lower ep additives and to meet the GL-5 specs, then they'd have to increase that, which then it would be higher in those additives than a GL-4. Also, a GL-4 doesn't have to be tested for thermal oxidation stability, channeling characteristics where the gl-5 does.

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Well, I do see gear lubes rated GL-4/GL-5.

Anyway, looks like there was no consensus back then.

[ January 06, 2005, 10:20 PM: Message edited by: moribundman ]

 

[moribundman]

Alright, more fact or fiction:

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"Modern gear lube additives contain sulfur-phosphorus components that are thermally stable, and are noncorrosive to bronze and other nonferrous metals."

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From: http://www.practicingoilanalysis.com/article_detail.asp?articleid=496&relatedbookgroup=OilAnalysis

 

[HardbodyLoyalist]

Let those who are convinced GL-5 lubes are safe in GL-4 applications put that stuff in their transmissions and then post a UOA after 12,000 miles.

Anyone brave enough to prove me paranoid is welcome to try. Until then, I'll stick with the straight GL-4 oils, thank you.

 

[Pablo]

A lube can be GL4 and GL5 rated.

Don't use a lubricant that ISN'T GL4 rating and you should be fine.

That said, don't use Mobil1 GL5 juice in your GL4 (requiring) transmission.....heed the man.

 

[moribundman]

I'm not using GL-5 in my transmission.

I simply would like to know if there is still no consensus. From what I can see, even Mobil can't decide, although their official stance is quite clear. As I've said elsewhere, the whole discussion seems to turn into a viscious, viscous circle.

There are no "true" answers.

 

[Bio-T]

GL-4 specific, GL-5 specific with a couple choices in weights and oil type:

http://www.specialtyformulations.com/index_files/Page457.htm

 

[HardbodyLoyalist]

The suspect the lack of consensus is strictly a liability issue. As a chemist, I suspect that most modern GL-5 lubes are safe against yellow metals. BUT, it's not like Mobil is going to tell me the exact composition of their add package, so there's no way for me to make a fully informed decision.

Anyway, I can easily envision a situation where the chemists and enginners at Exxon are telling the marketing and tech support departments that the GL-5 lubes SHOULD be safe in GL-4 applications. But then there's a lawyer down the hall saying "This is what class-action lawsuits are made of." The guy who actually makes the decision on whether to allow the company to make such claims unsurprisingly errs on the side of caution and, well, you end up with a situation where scientific facts are hard to come by nobody wants to put anything in writing.

As for those of us with limited resources, there's simply no way we can justify the risk of a $1500 transmission rebuild for the sake of debunking what may or may not be a myth.

And on and on it goes...

 

[moribundman]

HardbodyLoyalist, I hear what you're saying and I find it quite amusing that corporate greed is tamed by liability lawyers. I suppose it means the oil chemists are unable to convince the lawyers of the safety of particular products.

Vetteman, thanks for the tip, but I'm good for the next 50k miles. What got me started on this topic however, was the fact that I saw Specialty Formulations offering GL-4 lube, which previously had been labeled as sorta obsolete nowadays. But maybe that product is more aimed at worry-warts like me.

 

[Bio-T]

moribundman,

No, I would not call you a worry wart, just using what is spec-ed for your vehicle. And I agree with that in 95% of recommendations. I remember Mola Kule saying that he got into the business to produce hard to find lubricants. I think that this area he hit a home run.

 

[moribundman]

No worries there. I'm using what's called for in the manual -- even though that manual is almost 9 years old, and as we all know, things do change.

Good call on MolaKule's part to offer GL-4 lubes, as they are increasingly harder to come by.

 

[Fuelrod]

The problem may be the synthetic base stock "oil"..Dino gear lubes, being better NATURAL lubricants, can be formulated to GL-4 & GL-5 spec in the same product while synthetic base products can not..

I think what the Mobil rep was saying, "when we get our synthetic base fortified high enough so it can protect hypoid rear end gears, it will dissolve bronze and brass...so don't use it in transmissions...." IMHO...

 

[Alan]

I use M1 75W90 in my VW 02J transmission with no problems.Smooth shifting.This stuff didn't stink of additives like some dino 75W90's did.

M1 75W90 in GL-4 applications

 

[JohnBrowning]

sbc350gearhead hit the nail on the head!!! In order for a GL5 gear lube to be used in an application calling for GL4 it must be dual rated so would see GL4/GL5 on the side of the bottle.

Their are GL4 only products and GL5 only products still available. Speciliaty Products and Redline come to mind when GL4 only is wanted. Royal Purple has a dual rated product.

 

[Spitty]

For what it's worth: 10 years ago I re-built the rear end on my Triumph, and it was filled with Tech 2000 75-90 GL5 meets NM-1 also, the specs call for GL5, but Hey, Gear oil is Gear oil, GL5 must just be a bit better than GL4?
20,000 miles and 9 years on, the rear end is sloppy and and howls on bends, so the Diff is removed and inspected. Now, on this Diff the Diff carrier has fiber thrust washers on the sun gears that are well known to disintegrate, the planetary thrust washers are Yellow metal and are not 'known' to give problems, However on my Diff, the fiber washers are fine (thrust is still in spec) but the 'Yellow metal' washers are GONE, just a few shims in the bottom of the diff and a lot of GREEN gear oil.
It's too bad I did not get a UOA on this, but I did not know about BITOG back then.
Now the Diff runs with Penzoil GL4 synthetic and the Transmission Penzoil GL4 Syncromesh.
As far as I know, anyone who sells Penzoil products SHOULD be able to order these products.
Time tells all.

 

[Anthony]

My first car was bought brand new in 97 and my dad drove it for about 3 years and when i got my license in 2000 it was given to me. A 97 Nissan truck with a manual that called for gL4. The truck was given to me with a 100k on it and the manual transmission fluid had never been touched but it functioned perfectly.
Since i worked at valovoline i wanted to change the fluid and they convinced me that gl4 and gl5 didnt matter as long as i used the weight it called for which was 80w90.
So i put durablend gl5 in there. Not a good idea! It had a tendency to grind going into second and somtimes third and i thought it was a transmission problem not oil problem. So what did i do, go get more gl5 valvoline thinking im buying time until the transmission fails.

No help so i staated researching and settled for amsoil 80w90 that was speced gl3 4 and 5. It didnt help at all in fact it grinded more. Then i put redline mt90 and and problem solved.
It ran perfect up til 150k and then it was totaled

 

[1sttruck]

Hmmmmmmm... use a GL-5 lube in a vehicle which typically starts at $30k (diesel pickup), when a specific GL-4 synthetic is needed for warranty, and possibly for durability on a vehicle that you're planning on keeping for at least two decades. Might save $10 or even $20 every 30 thousand miles or so. Gee, that's a tough decision.

 

[TomH]

quote:

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Originally posted by HardbodyLoyalist:
Let those who are convinced GL-5 lubes are safe in GL-4 applications put that stuff in their transmissions and then post a UOA after 12,000 miles.

Anyone brave enough to prove me paranoid is welcome to try. Until then, I'll stick with the straight GL-4 oils, thank you.

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I've had the Mobil-1 75W90 gear oil in my 94 2wd Nissan truck since 99 in both the transmission and rear diff with absolutely no problems whatsoever with either. In fact, it shift as good now as when I got it back in 98. So there, I guess you can consider yourself paranoid!