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Aftermarket Gear Oil

by induction1, October 3, 2008



This does not necessarily relate to my Corolla, but I trust the advice on this site more than any other.

Anyhow, my other car specifies Nissan brand GL-5 80W-90 for the transfer case and differential, but I am looking at a different brand which is synthetic 80W-90 and also GL-5. I would never use a transmission fluid other than the factory spec (eg. Toyota T-IV for the Corolla and Nissan CVT for the car in question), even if other aftermarket brands say they're compatible, but can I safely substitute this different gear oil for the factory brand (for the transfer and differential) without fear of problems from different friction modifiers or other potential issues?

Thanks

I myself would use amsoil gl-5 if manufacturer calls for it.as much as i hate paying for amsoil , there are certain situations i find that it is a superior lubricant.especially. where you will never change it again unless you keep the vehicle another 5-10 years.here is another opinion.

GL-5:

So why is GL-5 so bad?

Oils are made from base stocks, refined and then mixed with additives to improve their performance. GL-5's incompatibility is due to the extreme pressure (EP) wear additives. To give the gear oil its EP rating, it's easiest to add a sulpher based additive like MoS2 (molybdenum disulphide) but the sulphur present in the oil (you can smell it) is responsible for eating the copper alloy used to make the synchros.

GL-4 differs from GL-5 by the amount these chemicals are mixed into the oil (1/2 to much less in GL-4). Since the same additives are present in GL-4, they will eat the synchros as well but at a point in time that is beyond the expected service life of the gear stack.

To get the GL-4 rating, the oil has to pass the ASTM D-130 test. This test determines how reactive the sulpher is against a polished copper strip. The strip is also subjected to heating to simulate the running conditions in the gear box.

Many people have put in a call to an oil manufacturer to ask them about the suitability of their GL-5 product for VW transaxles and received an inconclusive response. They may be told it's ok without any details to back it up. Likewise, they may have heard it's ok to use but the manufacturer won't confirm this because they haven't tested and proved it (cost and liability). The tech on the phone may not even know any better and since you are trying to match a modern oil formula to a 30 year old transmission, chances of getting an accurate confirmation is slim especially if his computer system comes up blank concerning your vehicle type.

To obtain GL-5 certification, the manufacturer does not have to pass the ASTM D-130 test. This is the main reason why you should avoid GL-5. So, if you put in a call to a manufacturer about their GL-5, that test result is what you want to verify.

Some people will claim that using GL-5 in a GL-4 spec transmission doesn't apply when the GL-5 is synthetic. This depends on the oil and cannot be generalized. However, it should be noted that many GL-5 synthetic gear oils do not use sulpher in their EP additive package and can pass ASTM D-130.

Even if the manuacturer states the gear lube is "non-corrosive", its viscosity index may be too slippery for the VW style synchros. This means that while the syncros won't corrode, the oil is not designed to grab the hub the way GL-4 does and the transmission will wear out another way.

As a final caution, some GL-5 formulas have been known to permanently coat the synchros in a VW manual transmission reducing its life by 50%.

So choosing a gear oil is both a matter of chemical and mechanical compatibility. In hindsight that seems obvious but the heat of the debate tends to cloud the issue.

when in doubt, use the dealer fluid. saving $30 on a fluid change vs how much does that transfer case and differential cost?

Redline 75W90 is an excellent GL5 rated gear lube. I run this in the diffs in my Jeep and it holds up to the heavy abuse dealt (quite a bit of rock crawling with lockers in both diffs).

friendly_jacek

Is this a truck? Do you tow? The reason I ask is because Nissan had a major issue with gear oils in titans recently. The factory fluid was inferior, often underfilled, and would cause overheating and premature diff failure while towing. They back spec'd those trucks with synthetic 75W140 gear oil.

Gear oils are poorly understood by motoring public and even car makers.

On a second thought, I just noticed CVT in your post, so probably never mind and any dino 80W90 or synthetic 75W90 GL-5 will work.

Bikeman982

I would think you could use any 80W-90 gear oil.

when in doubt, use the dealer fluid. saving $30 on a fluid change vs how much does that transfer case and differential cost?
Sorry about this late post reply; I haven't been around Corolland lately. I went looking for 80W-90 E50 gear oil for my Corolla; the local Toyota dealer says that it is so expensive (the genuine Toyota brand, that is) that they just use Mobil brand instead. They could special order the Toyota brand but the cost is prohibitive anyway ($26.00 per quart, and I need 6.2 quarts or 7 quarts). I'll probably use Amsoil, as soon as I can get the filler bolt off. Seems to be stuck . . .

 

 

Bikeman982

when in doubt, use the dealer fluid. saving $30 on a fluid change vs how much does that transfer case and differential cost?

Sorry about this late post reply; I haven't been around Corolland lately. I went looking for 80W-90 E50 gear oil for my Corolla; the local Toyota dealer says that it is so expensive (the genuine Toyota brand, that is) that they just use Mobil brand instead. They could special order the Toyota brand but the cost is prohibitive anyway ($26.00 per quart, and I need 6.2 quarts or 7 quarts). I'll probably use Amsoil, as soon as I can get the filler bolt off. Seems to be stuck . . .

 

Just use the Mobil brand instead.

 

 



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