Eduardo Sepulveda of Fortuneo Vital Concept, won the fourth stage and took over as the new leader of the Tenth Tour De San Luis.
Stage four was 139kms long and from San Luis to Cerro del Amago and had Dutchman Peter Koning (Drapac Pro Cycling) as its leader after he escaped to take a win on stage three by 1.37.
Twelve riders in Carapaz, Sivori, Najar, Guevara, Sarabia, Betancourt, Nodarse, Hornbeck, Alzate, Gaday, Ramos and Stacchiotti broke early and were 35 seconds clear before Guevara of the San Luis team took the first sprint of the day.
The gap was allowed to go out to eight minutes but onto Route 146, Costa Rican Paul Betancourt got away and his lead dropped from 5.15 to around four minutes.
The rest of the escapers caught up to him and there was a twelve man break which was three minutes clear with 74kms gone and the riders approaching the Toro Negro.
Through Toro Negro and their lead was back up to 3.30 before Guevara attacked again on a day where temperatures were around 36c.
The next attack saw Najar, Hornbeck, Alzate, Gaday, Ramos and Stacchiotti take control on the front of the race and they kept their lead going into the final kilometres with Najar taking the second sprint.
Onto the penultimate climb - the Alto de la Candela and the escapers were caught.
Astana attacked but Peter Sagan brought them back with Nairo Quintana and Vincenzo Nibali playing close attention.
Dayer Quintana led before a reduced peloton started on the Cerro del Amago which involved some nasty switchbacks.
With six kilometres to go, Janier Acevedo caught Dayer Quintana as did the Argentinian Eduardo Sepulveda, who took over the lead and opened up a lead of a minute over Dayer Quintana and 1.45 over Nairo Quintana, Lopez and Cardoso.
Into the final kilometre and Eduardo Sepulveda was clear and he rode away to win to give the team formerly known as Bretagne Seche Enviroment, their first win of the season in 4.00.35
Second was Javier Acevedo, some 34 seconds back with Roman Villalobos third, followed by Dayer Quintana and Miquel Lopez at 1.31.
Eduardo Sepulveda, now leads the race by three seconds from Dayer Quintana going into stage five.