Gearbox Oil change, 75W90 vs 80W90......

[rash_decision]

Hi all, looking for a little advice and opinions please. The wife has a 2012 Fiat 500 1.2, with 96k miles, and in driving it last week I noticed the gearbox ‘slightly’ noisy. Not bad by any means, but as a ‘tinkerer’ and in the interests of giving myself something to do over the holidays, decided to change the gearbox oil.

The correct grade is 75W90 but I have a couple of litres of 80W90 mineral gear oil in the garage.

I’m of the opinion this would be fine, and probably help the minor wear that I could hear, with this oil being ever so slightly heavier than the 75W specified. Any opinions or advice appreciated before I dump the current oil, should I go ahead or get some 75W delivered?

Thanks in advance.

[Chris32345]

It's will likely need a input shaft bearing seems to be a common failure on these boxes


As for the oil I doubt it will make much fo a difference

[GreenV8S]

It will be a bit thicker when cold, which might affect the gear change quality. Once it has come up to temperature, there will be no difference (they are the same hot grade).

[Mave]

Main thing about gearbox oils IMHO is making sure it is the correct chemical spec rather than the correct viscosity - not all synchros are compatible with all oil types

[Willy Nilly]

Mave said:

Main thing about gearbox oils IMHO is making sure it is the correct chemical spec rather than the correct viscosity - not all synchros are compatible with all oil types

I had the transmission oil changed on my Jazz because of the reputation for them to fail, which was supposed to be caused by some swarf that hadn't been flushed out when they build them. Annnyway, the oil he put in i didn't agree with it and it was a bh to shift unless it was very war, which it often isn't. So I had him change it again for something different and it's fine now.