I switched to Brad Penn 15-40 as it's made with all the zinc old oils used to be made with. I get it from a local engine builder for $75 a case, which is less than the cost of other good oils and a bottle of zinc additive. I'm saving probably a couple dollars per qt. on every oil change.
I recently also found 30 cans (yes cans!) of NOS 20-50 Valvoline Racing Oil on Craigslist locally for $4 a qt., so I bought all of that too! Great oil at a very low price!