What year are the 164s do you have? I've been told that it was mostly 91s, and more than likely the S models having bad oil rings.
Our 89 Milano and 94 164LS use no oil at all between 5k-7k mile changes, but the 91S drinks it prodigiously, 300-400 miles to the qt, depending on how/where I drive. Always has, evidently since new (I bought it with 40k miles on it).
89 Milano (wife's daily driver since 1989, Shankle Sport)
91 164S (my daily driver since 1994)
94 164LS (~Q) (trip Alfa since 2000)
72 Morgan 27 (water time since 1976)
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