Valencia, who stay third, have also enjoyed a strong start under new coach Jose Bordalas but leave hugely disappointed not to have taken three points from this game, let alone one.
Madrid sit two ahead of Atletico Madrid after Atletico were held to a goalless draw by Athletic Bilbao on Saturday, and six in front of Barcelona, who have two games in hand, the first against Granada on Monday.
Benzema already has six goals this season but the real bonus for Ancelotti has been the form of Vinicius, who has five goals himself, already more than the 21-year-old managed in the whole of the last campaign.
Both teams were hampered by early injuries as Real Madrid’s Dani Carvajal had to be replaced by Lucas Vazquez while Valencia lost both Carlos Soler and Thierry Correia, with Yunus Musah and Toni Lato coming on.
Valencia were faster and more aggressive and they had the better chances too, Gabriel Paulista going closest in the first half with a header from a free-kick.
Duro should have scored seconds after half-time when he ran in behind but Thibaut Courtois saved again and then Duro was thwarted by the Belgian for a second time after a mistake from Casemiro in midfield.
Finally the pressure paid, as Vazquez turned away from a deep cross from the right and the ball skidded off his back to the foot of Duro at the back post.
Duro still a lot to do with the bouncing ball but hooked a superb shot past Courtois into the far corner.
Summer signing Eduardo Camavinga replaced Casemiro and Rodrygo came on for Modric, with the Brazilian almost levelling for Madrid when he met Vazquez’s cross at the front post.
Valencia were dropping deeper and deeper and in the 86th minute they caved, Benzema showing impressive composure to turn and tee up Vinicius, whose shot nicked off Dimitri Foulquier, wrongfooting Giorgi Mamardashvili and flying in.
Madrid were not finished yet as Valencia conceded again two minutes later. Vinicius returned the favour by curling in a cross from the left, as Benzema nipped between Gabriel and Mamardashvili to head in.