Los Blancos recorded a straightforward win at home against the relegation strugglers to sit provisionally 13 points clear of rivals Barcelona at the top of La Liga
Los Blancos were ahead in the sixth minute through Cristiano Ronaldo's header before Racing went down to 10 men after the referee awarded Domingo Cisma a second yellow card. Madrid were 2-0 up at the break when Benzema netted in injury time.
Angel Di Maria marked his return from injury with a superb strike in the 73rd minute, before Benzema added his second and Madrid's fourth in the 89th minute to put the icing on the cake for the home side ahead of Tuesday's clash at CSKA Moscow in the Champions League.
The win gives Jose Mourinho's men a 13-point cushion at the top of La Liga with rivals Barcelona not in action until Sunday evening, when they face a tricky test against third-placed Valencia.
Madrid made a lively start to proceedings and could have found themselves a goal to the good in the fifth minute. Kaka's inviting corner was met by a downwards header from Ronaldo who could only watch on in despair as the ball struck the post before the visitors cleared the danger.
However, Mourinho's side only had to wait another minute before finding the back of the net. Benzema's through ball fell to the feet of Kaka, who saw his shot parried by Tono. The quick-thinking Brazilian then headed the rebound across the Racing goalmouth for Ronaldo to nod home for his 35th goal of the season in 34 appearances in all competitions.
The visitors' fortunes turned from bad to worse on 39 minutes when they were reduced to 10 men after Domingo Cisma was shown a second yellow card. The full-back was adjudged by the referee to have intentionally blocked Ronaldo's cross with his hand, but replays showed the former Almeria man was harshly given his marching orders.
Madrid doubled their lead with the last action of the first half when Benzema netted in added time. Xabi Alonso was alert to slide a set piece through to the Frenchman, who clipped an effort over the head of an onrushing Tono with Sergio Ramos on the line to make sure the ball ended up in the back of the net.
The home team looked comfortable throughout the second period and added a third in the 73rd minute. Substitute Angel Di Maria, making his first appearance for Los Blancos in 12 games, cut infield from the right wing before smashing the ball past Tono and into the far corner of the net from the edge of the box.
Benzema added his second of the game in the 89th minute after the striker picked up a rebound from Di Maria's parried effort. The former Lyon striker smashed the ball high into the goal via a deflection from Bernardo as Madrid easily secured all three points.
Madrid now head to Russia, where they will face CSKA in the first leg of their last-16 Champions League encounter, while Racing are next in action in La Liga versus Sporting Gijon on February 25.