Correct gearbox oil for 6 speed 1.33

[Fungus007]

I've ready a few post here that the factory recommended oil to use is the  2.5 liters of SAE 75W GL-4 monograde full synthetic and putting in multi viscosity oil will cause long term damage. 

However the only mono grade oil 75w gl-4 oil I could find is this brand called SWAG and doesn't indicate whether its full synthetic. 

So my question is should I go with a know brand like Red Line MTL 75W80 GL-4 or Penrite 75w85 gl-4 full synthetic or the Swag brand? 

Mt gearbox is also making a slight whirling sound at highspeed between 80/85km/h so maybe in my case having the multi grade thicker oil at normal operational temp is good? 

 

[Mark_P]

The Safety sheet doesn't say if it's full synthetic - https://cdn.pkwteile.de/uploads/hazard/passports/2128211-EN-1.pdf

Autodoc does say it's compatible with the IQ - https://www.autodoc.co.uk/swag/2128211

The swag website swag.de doesn't say anything either.

Edited October 31 by Mark_P
added more to the post

[Fungus007]

2 hours ago, Mark_P said:

The Safety sheet doesn't say if it's full synthetic - https://cdn.pkwteile.de/uploads/hazard/passports/2128211-EN-1.pdf

Autodoc does say it's compatible with the IQ - https://www.autodoc.co.uk/swag/2128211

The swag website swag.de doesn't say anything either.

But is full synthetic recommended by Toyota in the official manual? 

Will going muti grade oil really be an issue if its only 75w80? 

[Mark_P]

Do you have the manual.  It doesn't mention synthetic oil for the transmission. Synthetic is for the engine.

If anything, search for the Toyota Genuine Transmission Gear Oil LV  https://toyotadirectparts.co.uk/parts/toyota-universal-parts/toyota-gear-oil-75w-lv-manual-transmission/