mrf94 said:
My problem at the moment is finding the ZC 90 or equivelent for the gearbox
Cut and pasted again. From thread 25663, this time:
The correct FIAT oil is their own "ZC 90"
There have been a number of discussions in the past about what (else) is suitable, as Haynes suggests you can use engine oil.
The FIAT stuff is GL1 (very early gear oil specification, with little in the way of additives, apart from something for "anti wear").
According to the site, here, there are different viscosity numbers for the same grades of oil depending on if it is rated as engine oil, or gear oil:
gear oil numbers are higher - 90 is around the 20(W50) mark as an engine oil, so one up for Haynes.
You don't want a gear oil which is designed for hypoid (back axles) use as the sulphur additives can eat bronze parts in some gearboxes...
IMHO, you don't want the latest specification (GL4 or 5) gear oil as the antislip additives will stop your synchromesh from working properly: it needs some friction to get the bits to run at the same speed and not get a crunch (especially into third - but if it's crunchy now, an oil change is unlikley to bring the synchro back to life).
There are many who use GL5, and say the results are wonderful...
So I suppose the short answer is:
FIAT stuff is the best for the job, but (relatively) expensive in the UK.
Some 20W50 engine oil would probably not do any harm - as per "Haynes" - but you don't have the "antiwear additive".
"Wilko" (Wilkinsons) sell Comma branded (GL4) at 2.09 UKP litre in 1 litre tubs - you'd need 3 for a complete change of oil, and still have some left over.
Or, you could go to one of the Countrywide Farmers shops here and get 4 litres of Q8 branded gear oil (GL5 though), and some engine oil too, for about 10 UKP a tub. The last basic, 15W 40, engine oil I got there (20-01-2005) was just over 6UKP for 4 litres.