Hmm - my spanner in the works !
Having owned both twinspark, 12v V6 and now 24v V6 164's, the answer that will satisfy you most is - actually the cheapest, nastiest (well not the nastiest, but certainly cheapest!) oil you can find.
A filter should by definition last about 2 oil changes on average, and you can wash them out with car wash as semi-non polar soap, and rinse with distilled water is your feeling really cheap. it works too.
But for the oil - the older the alfa, the thicker the oil. While they are new, they can legitimately use Shell 5w-40, the Ferrari approved oil. This especially holds true of the v6's, which while having the Busso hemi-head, are still essentially Dino v6's. The twinsparks do not like the weak oil consistency much. New means less than 100,000 km's, as an Alfa is only 'broken in' by this point.
After 100,000 I have found ordinary 20w40 is ideal, as the alfa will need a change every 5000-10,000 k. why the variance ? If the oil is ok, then startup oil pressure on both twinspark and V6 is at 4, and then once the engine is toasty, settles down to 2 on the gauge.
How can you tell if the oil is f**cked ? Denaturation point is when on startup cold the pressure does not exceed 3.5 on the gauge, and then when toasty appears to drop completely to one or below ! this is a sign that there is still oil in the crank, but that its well past it. Replace immediately.
Nice thing though - 20w40 is a cheap oil, and as long as it meets an SAE standard your fine. Don't even bother with name brand - often they are rebranded Caltex or Shell.
After 175,000km - 200,000 km, the Alfa will desire 30w50 or some high viscosity oil. This is cheaper yet - yep, low grade diesel oil. With advancing wear (and a reluctance to get new rings), a thicker oil guarantees the engines life. I've never owned an Alfa with that many k's, but the guys in the local AROC with older twin cams have found this works excellently. Consequently, the Alfa needs a bit longer to get toasty, say 7 mins as opposed to 5. But thats ok too.
So despair not ! its easy to get a good life out of the engine, and Twinsparks are particularly bulletproof.