Reigning World Rally champion Sebastien Ogier was the early leader of the Rally Argentina after winning the first super stage in Merlo.
The Volkswagen Polo R driver was quicker than team-mate Andreas Mikkelsen and Citroen's Northern Irish driver Kris Meeke by two-tenths of a second.
"It's going to be a long weekend with some very tough stages but that's the same for everyone," said the Frenchman to the World Rally website.
Ogier has been dominant so far, winning in Monte Carlo, Sweden and Mexico.
Jari-Matti Latvala was a tenth of a second further back, with Hyundai team-mates Dani Sordo and Thierry Neuville completing the top six in their i20 World Rally Cars.