300LS 75-90 safe for synchros and brass ?

[headoff93]

Hello.
Unfortunately i put Motul 300LS 75-90 in my M32 gearbox with drexler LSD, it's a FWD car.
I didn't check about the GL standard, because friend is driving with the same oil.
Now after 2000km and two track days I just saw the "GL5" on the bottle.
For now I don't have any problems.
Also have Millers CRX LS 75w90 NT+ in the garage, which is gl4/gl5.
Should I change the oil and flush the gearbox ?
Motul says "mechanical transmission, synchronized or non synchronized gearbox"

 

[kschachn]

@MolaKule

 

[RallyXaDSM]

The Motul TDS says "Suitable for any type of seal and any type of material used in gearbox and limited slip differential design", but there's no listed ASTM D130 result or specific mentions of yellow metals. It's probably safe for direct contact, but being GL5-only there's no guarantee that you won't still experience the plated EP additives gradually eroding the synchro surfaces (sort of like what happens when you peel tape off of cardboard). Millers seems like a safer option here due to also being GL4. You could alternatively just run a high quality GL4 and use whatever LSD additive Drexler recommends.

 

[MolaKule]

I think both gear oils should be sufficient but I would shorten your OCI due to your driving routines.

EP additives are buffered against copper-alloy attack.