River's impressive win comes just three weeks before they host archrivals Boca Juniors at the Monumental in the first "Superclasico" since River lost 2-0 at La Bombonera in May 2011 and were relegated a month later.
River's last home win in the top flight was a 1-0 victory over Banfield in April 2011. They lost their next home game to Sunday's opponents Godoy Cruz and began the downhill slide towards relegation.
But they have suddenly clicked, scoring nine goals in two matches while conceding none, adding Sunday's five-goal spree to last weekend's 4-0 victory at title holders Arsenal.
With each successive goal on Sunday, a heaving Monumental chanted River's favourite anti-Boca songs anticipating their next home match - the biggest club game on the Argentine football calendar.
Boca's 3-1 loss at Belgrano in Cordoba earlier in the day made Sunday's victory all the sweeter for River's fans.
Coach Matias Almeyda appears to have finally hit on a successful counter-attacking formula which brought an opening goal in the ninth minute for midfielder Martin Aguirre from Rodrigo Mora's low cross to the near post.
River's key player, central midfielder Leonardo Ponzio, then marked his 100th game for the club with a cheeky goal from a free-kick 30 metres out three minutes later.
"We deserved something like this at our ground. We won well against tough opponents," Almeyda told reporters.
Winger Carlos Sanchez ran onto substitute Rogelio Funes Mori's pass to score the third just past the hour and Mora netted the fourth in the 63rd minute after Ibanez spilled a cross.
Sanchez saved the best for last, lobbing Ibanez from the edge of the box in the 75th minute as River climbed to eighth with 15 points from 10 games just past the halfway mark in the 19-match "Inicial", the first of two tournaments in the season.
Newell's Old Boys are top with 22 points after their 1-0 home win over Velez Sarsfield thanks to Maxi Rodriguez's goal after 30 seconds.
