I think its safe to assume that the OP will be coming from the North to Brazil, and then come down to EZE. This is therefore a INT to INT connection... even though its technically inside MercoSur.

Argentine customs does not give a hoot about alcohol..... if you were bringing in super expensive Whisky or Cognac, they may want another look, but I think that a few bottles of high-octane lighter fluid made in Brazil will not get anybody´s attention.....