I used a synthetic oil in many of my Fiats with great results. In my Alfas 33's (3 number) I found it better when starting (slicker) selection of gears when cold but more difficult when the oil was hot.
On the Weekend I used a partially syth oil in my 146 boxer and found a huge difference. Maybe this was down to a full Alfa serice history and just under 2 litres of oil in the gearbox:-/
Also thankfully I checked the belts 1 changed at 56k the other original! at 120k wow!