URGENT ADVICE PLEASE (GEARBOX OIL)

[Sev131]

What oil do i use in my 131 sport gearbox?

I can't find any previous posts.

Regards

[ros]

According to the haynes manual for manual transmission SAE 80/90 not EP

[Thotos]

There's a long discussion thread on this on which we failed to reach agreement from what I remember. But I've researched this a lot so here's my two pennies worth (even though I know some people here will disagree):

The 131 gearbox should have a SAE90 gear oil but not an EP gear oil as the Extreme Pressure additives in EP oil can damage the bearings in the gearbox. Fiat recommend their own ZC90 gear oil which should still be available from any Fiat agent. Now an SAE90 gear oil has the same viscosity as a 30W engine oil so you could simply fill your gearbox with a straight 30W engine oil. In fact Fiat in the UK used to recommend the use of multigrade engine oil in the gearbox of most Fiats including the 131. That's perfectly acceptable practice but if you decide to go the multigrade engine oil option get 20-50 or similar and don't go for the rather thin modern   0-40 oils.

[mirafioriman]

I think mine has Castrol GTX in it. But as many of you know mine does very few miles

[Sev131]

Brilliant!

I know what to get now tommorow.

I need to get this car ready for friday 6am! Gearbox bellhousing bolts in tonight, the rest to do tomm- including fitting a 4 branch and Janspeed exhaust system done about 2000 miles. Another good prop as the centre bearing rubber has broken, alternator and final carb balancing to do as best for now. I've just refurbed the 45's and fitted proper Misab spacers/rubbers/washers and manifold studs. What a previous bodge job on twin carb fitment. 

Thanks to all for a very quick response tonight.

[theredx19]

Sev get the zc oil as this very important for the preservation of the synchro mesh system as this is where the ep oil has an issue as it will not let the synchros slow before meshing.... wont affect the bearings as these are case hardened and for them oil is oil. As regards a discussion Fiat Italy spent Billions upon Billions of lire developing their gearboxes and there is a very good reason why they said only use a zc oil as viscosity is one aspect of oil but there are many other unseen aspects to oil.....