Miller's gearbox oil

[Porkscratching]

Hello, I'm in need of gearbox oil and I've found 5litres Millers EP 80w/90 for £12.70.
My question; is the "w" in the spec of concern, ie is this oil compatible?

I'm sorry if this seems a silly question but the box rebuild was a significant cost.

Before anyone asks, yes it's 5ltr and yes it's £12.70.

Regards,Max.

[ZsZ]

If it is GL4 (I assume it is) then it is the OE oil recommended viscosity.

However nowadays better 75W90 oils are available. (Like Castrol Tansmax Manual with VW spec approval)
Those make gear changes in cold temps (below 10°C) smoother.

[Porkscratching]

Thanks Zoltan. Yes it's GL4 mineral. The box builder was pretty emphatic that I shouldn't use synthetic oils as they effects the coatings on the syncro rings .
If the "w" part of the spec is of no consequence then I think I'll go for it. I'm hoping it just means winter.

I'm lead to believe that Millers are a reputable brand.

[ZsZ]

No probs.
The additives in GL5 oils could affect the brass pieces like synchroniser rings, but it depends on specific brands of oil.
You will be fine with that oil IMO.
It is even better if you add Molyslip GM6RA additive as Aidan recommends.