Wikipedia, and Bob the oil guy, just to quote a couple of nontechnical sources, both say the following about double clutching, "when done correctly it prevents wear on the "synchros"". That's what I was taught as well. At any rate, works well for me.
So "Indeed, you add wear to the synchronizers every time you do that" may not be correct.
If done perfectly, it's as if the synchronizers are not even there, as I used to learn when I drove my father's old WWII weapons carrier truck with a smash gearbox.
What double clutching can do is add more wear to the clutch disc and levers, rods, etc, being used more often. However, in my case with my 91S for instance, the clutch disc lasted 191k miles, and when the clutch was finally replaced, the synchros and everything else were still fine. So that's obviously not a worry.
My own impression has always been that, esp with old Alfa gearboxes, even from new, clod drivers could wreck synchros, esp 2nd gear, by trying to force the shift, ie, not using the patented "Alfa hesitation shift". I always used that, as taught to me by Carlo, and I never had a bad 2nd gear synchro in any of my Alfas, at least none that I can remember.
"just to prove to myself that at 51 I can still do it"
Hah, you youngsters! At 78, I still have fun doing it, pretty much every time I drive. I mean, why not? It's fun, and a skill I don't want to lose by being lazy. Just for kicks, sometimes I even go down through the gears from fifth into first that way. It's easy and satisfying. You can just feel/hear the gears and engine interacting at your touch.
1989 Milano, Shankle Sport
1991 164S, stock
1994 164LS (~Q)
1972 Morgan 27
previously owned since 1964:
62 Morris MiniMinor 850, 67 Austin 1275 Cooper S (Downton 3/4 race), 64 Giulia Sprint GT (1st red one made), 72 Fiat 128 Sedan, 75 Alfetta Sedan, 78 Alfetta Sedan, 78 GTV, 81 GTV6, 86 GTV6
Last edited by Del; 04-22-2019 at 04:42 PM.