Some interesting info here ~ scroll down to list of 22

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2556125

        Nice image here that shows the CopperStripTest classifications

http://www.machinerylubrication.com/Read/28958/ep-additives-effects

On 28 Aug , 2012, at 1:10 AM, Gene P wrote:

> [clip clip, lots of folks wrote]
>
> Very confusing issue and discussion.  Just a few brief points:
> 1)  The German mechanic that installed a rebuilt transaxle for me 9
> years ago said "use GL-4 oil only, NOT GL-4/GL-5, GL-4 ONLY. Wrote it
> that way on the invoice.
> 2)  GoWesty is not everyone's reference of choice, but they still
> recommend and sell MT-90.
> 3)  The Redline website has an application guide: plug in your vehicle
> (for me an 87 2.1 hardhat) and the recommended transaxle oil is MT-90.
> 4)  Following a discussion like this about 6 months ago, I called
> Redline and the person I talked to knew nothing about a formulation
> change and could not imagine why one of their reps would say MT-90 is
> not recommended for our vehicles.  When I asked about the "not for
> hypoid differentials" statement on the site, he said Hypoid
> Differentials are not the same as our Hypoid Transaxles and went into
> some stuff about shaft angles and pressures and whatever that was way
> over my head.
> 5)  A  clip from a dandy 2-page technical article on Redline's
> website:
>     "GL-5 gears oils which are required in hypoid differentials are
> not
> used in most synchromesh transmissions because the chemicals used
> to provide the extreme pressure protection can be corrosive to
> synchronizers, which are commonly made of brass or bronze. Typically,
> the use of a GL-5 lubricant in a synchromesh transmission will shorten
> the synchronizer life by one half."
>
> So ... I ain't an expert, but I did enough homework to be comfortable
> continuing to use MT-90 and to throw out a caution about any GL-5.
>
> Your wives' tales may vary ...