To add a bit more
To add a bit more to JRVs most accuate assesment..
A very contoversial subject indeed....
Background: I have rebuilt three Ferrari gearboxes now...and most recently the one from my BB. They are all somewhat similar in design, specifically in the design of the shift rails. In my opinion, they all are a bit hard to get into second gear for the same reason....the shifter rail is subject to hydraulic locking in the case bore, just by the design. So...with a thinner flowing oil, when cold, it will be easier to engage second gear...
But, thinner oil is not always better and can cause other problems, that may have not been evident before the "new" oil change.
I rebuilt my 365BB gearbox last Summer...other than some brass in the bearing cages, the synchros are of steel or iron alloy. Your 308/328 gearbox is of similar construction and materials.
I used Mobil 1 in the gearbox, for a while, prior to the rebuild....Although it did shift smoother, I could "beat" the synchros, if I shifted even slightly quickly....
Currently, I'm running Royal Purple 75-90W, a GL-5 spec oil...Shifts smooth, with little to no 2nd gear nonsense. I contacted both Mobil and Royal Purple about the semi-unique charateristics of the Ferrari gearboxes. Based on their responses, I did not feel comfortable using Mobil 1 any longer. I feel that any GL-5 oil, such as Penzoil 4096...or Royal Purple is a good choice.
To clarify some popular mis-conceptions:
-If a syncro is bad...snake oil will not fix it.
-No matter what type of (correct) oil you use, frequent changes make for easier gear changes.
-Regardless of oil type, when the weather gets colder, these boxes are going to be a bit more difficult to engage gears in...
-IMO, this diff chattering issue is way overblown. I've owned four F-cars through the years...and never heard a peep from the diffs, no matter what "blend" of oil was installed.