auszookers.com :: View topic - Is there much difference between 75W-90 and 80W-90?

TheOtherLeft wrote:

I am about to change my transfer gear oil which the owner manual recommends 75W-90. However I have a few litres of Castrol EPX 80W-90 leftover from doing my diffs.

Is there much difference between 75W-90 and 80W-90?

Can I use the 80W-90 in my transfer?

The question that needs to be asked is what spec oil are we discussing - EP? GL4? GL5? There's more to it than just the weight or thickness of the oil.

Differentials will usually take an EP (extreme pressure) or GL5 oil, and putting that in the transfer case of a GV, where GL4 is what's required, can cause problems with the brass synchro ring (GV's have a syncho ring in the transfer case, Samurai/Sierra/Vitara don't).

On the other hand - if the oil says it's safe for use with copper, brass, bronze or yellow metals - then go right ahead and use it.

Author:	TheOtherLeft [ Fri Dec 24, 2010 5:38 am ]
Post subject:	Is there much difference between 75W-90 and 80W-90?
I am about to change my transfer gear oil which the owner manual recommends 75W-90. However I have a few litres of Castrol EPX 80W-90 leftover from doing my diffs. Is there much difference between 75W-90 and 80W-90? Can I use the 80W-90 in my transfer?

Author:	steak_knife [ Fri Dec 24, 2010 5:39 am ]
Post subject:	Re: Is there much difference between 75W-90 and 80W-90?
80w90's fine...

Author:	Che [ Fri Dec 24, 2010 5:48 am ]
Post subject:	Re: Is there much difference between 75W-90 and 80W-90?
Did this yesterday, 75-90 is bloody hard to find. I used the castrol 80-90 stuff you've got. My manual gives this the OK too, but I got a 90 Sierra.

Author:	TheOtherLeft [ Fri Dec 24, 2010 5:49 am ]
Post subject:	Re: Is there much difference between 75W-90 and 80W-90?
Mine's a 2002 auto GV.

Author:	TheOtherLeft [ Fri Dec 24, 2010 5:53 am ]
Post subject:	Re: Is there much difference between 75W-90 and 80W-90?
che_guitarra wrote: Did this yesterday, 75-90 is bloody hard to find. CASTROL SYNTRAX 75W-90 and CASTROL MULTITRAX.

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Author:	fordem [ Fri Dec 24, 2010 12:56 pm ]
Post subject:	Re: Is there much difference between 75W-90 and 80W-90?
TheOtherLeft wrote: I am about to change my transfer gear oil which the owner manual recommends 75W-90. However I have a few litres of Castrol EPX 80W-90 leftover from doing my diffs. Is there much difference between 75W-90 and 80W-90? Can I use the 80W-90 in my transfer? The question that needs to be asked is what spec oil are we discussing - EP? GL4? GL5? There's more to it than just the weight or thickness of the oil. Differentials will usually take an EP (extreme pressure) or GL5 oil, and putting that in the transfer case of a GV, where GL4 is what's required, can cause problems with the brass synchro ring (GV's have a syncho ring in the transfer case, Samurai/Sierra/Vitara don't). On the other hand - if the oil says it's safe for use with copper, brass, bronze or yellow metals - then go right ahead and use it.

Author:	TheOtherLeft [ Fri Dec 24, 2010 6:41 pm ]
Post subject:	Re: Is there much difference between 75W-90 and 80W-90?
fordem wrote: TheOtherLeft wrote: I am about to change my transfer gear oil which the owner manual recommends 75W-90. However I have a few litres of Castrol EPX 80W-90 leftover from doing my diffs. Is there much difference between 75W-90 and 80W-90? Can I use the 80W-90 in my transfer? The question that needs to be asked is what spec oil are we discussing - EP? GL4? GL5? There's more to it than just the weight or thickness of the oil. Differentials will usually take an EP (extreme pressure) or GL5 oil, and putting that in the transfer case of a GV, where GL4 is what's required, can cause problems with the brass synchro ring (GV's have a syncho ring in the transfer case, Samurai/Sierra/Vitara don't). On the other hand - if the oil says it's safe for use with copper, brass, bronze or yellow metals - then go right ahead and use it. Hmmm, interesting. The manual states GL4 for the transfer but the EPX 80W-90 is GL5. I thought since GL5 is better then GL4 then that would be OK in my transfer... I guess not. Do you what the difference is between GL4 and GL5?

Author:	Bruce [ Fri Dec 24, 2010 7:14 pm ]
Post subject:	Re: Is there much difference between 75W-90 and 80W-90?
GL-4 and GL-5 are standards set by the American Petroleum Institute for gear oils. GL-4 are intended for axles with spiral bevel and hypoid gears operating under moderate to severe conditions of speeds and loads. They are also suitable for sychronized manual transmissions when MT-1 gear oils are NOT recommended. GL-4 should be used in limited-slip differentials. The GL-4 generally indicates "Limited Slip" properties in the gear oil; sometimes abbreviated as LS. GL-5 is indicated for high-speed/shock loads and low-speed/high-torque conditions. GL-5 also has multi-purpose or mild EP (extreme) properties too. GL-5 is often seen with the MT-1 designation too. MT-1 indicates lubricants intended for NON-sychronized manual transmissions. MT-1 indicates the additional additives necessary to protect against thermal degradation, component wear and oil-seal deterioration which are not requirements by GL-4 or GL-5 approval. GL-5 is not the latest and greatest improvement over GL-4; unlike oil classifications where higher classification numbers mean tougher standards and backward compatiblity Read more: http://wiki.answers.com/Q/Whats_the_dif ... z1942BQ88S

Author:	fordem [ Fri Dec 24, 2010 8:20 pm ]
Post subject:	Re: Is there much difference between 75W-90 and 80W-90?
That sounds kind of backwards. GL5 oils contain more EP (extreme pressure) additives than GL4 and are usually specified for gearboxes or transmissions that have hypoid cut gears - think the ring & pinion in a typical differential where the drive turns through 90*. One of the common EP additives used to be sulphur, and under high heat, high load conditions, the sulphur would form acidic compounds that would attack the softer yellow metals such as brass or bronze, commonly found as syncro rings or hubs. For this reason it is common to see GL4 oils specified in your 5 speed transmission, which has brass synchro rings, but no hypoid gears, and GL5 oils in your differential which has no syncro rings, but does have hypoid gears. MORE EP additives = LESS sliding friction, but, because of the gear design in the transfer case, there isn't that much sliding friction anyway, and since there is brass, the nusing a GL5 oil may not be your best choice. Here's the kicker - some GL5 oils are safe for use in transmissions containing brass, because they do not use sulphur as an EP additive - check the spec on your particular GL5 oil and be guided accordingly.

Author:	Bruce [ Fri Dec 24, 2010 9:13 pm ]
Post subject:	Re: Is there much difference between 75W-90 and 80W-90?
Owell the google 5 sec look must be wrong then.

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