1.9tdi GEARBOX oil change. What oil?

The Haynes manual suggests G50 75w-90

The part number I got from Audi was G 052 911 A2 Which when I look at it on Ebay comes up as 75w-80.

Is there much difference in 75w-80 and 75w-90?

Also I've heard that using GL-5 oil instead of GL-4 oil kills the syncro mesh.

Febi oil on Ebay: (GL-5 oil)
https://www.ebay.co.uk/itm/Febi-Gea...016677&hash=item5903bc9955:g:oKoAAOSwfVldQlt7

Link to thread:

http://www.audifans.net/ftopict-35503-.html

Does anyone with more knowledge than I have any helpful input?

Would GL-4 75w80 be the best oil to use?

Many thanks

Andy

Thanks for the reply

I'm not sure if the FWD boxes are spec'd for GL-4 or GL-5 tbh, but when I asked around a couple of years ago I remember someone saying "Changing it could do more harm than good" Which I thought was an odd thing to say, and why I haven't done it before. Anyway last week I was under the car and thought I'd check the level. I could feel the oil through the fill hole in the side of the box, but it did come out pretty black, and the car doing 216k miles I'm thinking its definitely due a change.

Anyway reading up recently I found the GL-5 issue about eating syncro mesh on a Clio forum.

See here:
https://cliosport.net/threads/1-2-gearbox-oil-confusion-75w80-or-75w90.582913/

After that I thought well maybe its just rubbish french engineering, so dug a little deeper and found the audi link above:

http://www.audifans.net/ftopict-35503-.html

Quote:

"I used 75w-90 GL5 gearbox oil as recommended by GSF, Eurocarparts etc and after 2000 miles my syncros were eaten away, crunching into 4th etc etc changed back to genuine oil and still a crunch but it has not got any worse"

I guess the OEM oil will be the right spec, but it would be nice to know for sure.

Definitely surprised by the colour of your oil and it looks more than 2.5 litres?

https://www.rymax-lubricants.com/blog/the-differences-between-gl-4-and-gl-5/

Bottom paragraph on this page:

"The main difference between GL-4 and GL-5 gear oils is the amount of EP additives. Sulphur/Phosphorus containing products are used as EP-additive. This additive has the purpose to prevent the occurrence of micro-welds on the gear flanks at the local high temperatures which prevail in EP circumstances (temperatures well in excess of 800℃!) GL-5 has roughly twice the amount of EP additives compared to GL-4, which is why it is often used in high-pressure circumstances such as in a front axle and rear axle differential.


Sulphur/Phosphorus additives however have an unfavourable property: they can react aggressively towards bronze and copper. This can be disastrous for the synchromesh rings of a gearbox. Therefore it is not recommended to use GL-5 in a gearbox unless the manufacturer allows this.


To conclude:


• GL-4 is suitable for hypoid gear service when they are under severe service but are without shock loading.


• GL-5 is suitable for hypoid gear service under severe service and shock loads and not for use in a gearbox."