The Portuguese eclipsed Lionel Messi's double in Barcelona's 2-0 win at Real Zaragoza earlier in the day and helped restore Real's one-point lead over their arch rivals at the top of La Liga.
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Real have now scored 16 times in three La Liga outings and former Inter Milan and Chelsea coach Jose Mourinho already appears to be working his magic after only a few months in the Spanish capital.
Ronaldo is La Liga's top scorer with nine goals, including eight in his last three games in the competition.
"It's great to score four and help out but the main thing is the team," the winger said in a television interview.
"As the coach said the other day, we can't be too euphoric because there is still a long way to go in the season."
Although Real have yet to play any of their potential rivals, they are in the sort of devastating form that could end Barca's two-year grip on the title and next month's "Clasico" between the teams can gauge how far Mourinho's team have come.
Argentina striker Gonzalo Higuain opened their account in the 10th minute and Ronaldo followed up with two smart finishes in the 15th and 27th.
He completed his hat-trick two minutes into the second half and scored a fourth from the penalty spot in the 55th before Mesut Ozil made it 6-0 eight minutes later.
Racing, down in 16th position, pulled one back in the 73rd when a shot by Papakouli Diop went in off Markus Rosenberg's back.
Unbeaten Real have 20 points from eight games.
Valencia are fourth on 16 after they slipped to a second straight defeat, losing 2-1 at home to Real Mallorca in Saturday's late match.
FLAILING ARM
Earlier, Messi registered his second double in a row to give Barca victory against 10-man Zaragoza at the Romareda.
Fresh from his two goals against FC Copenhagen in the Champions League on Wednesday, the Argentine broke the home side's stubborn resistance with a clinical finish in the 42nd minute.
Spain striker David Villa, playing against one of his former clubs, took out three defenders with a surging run and knocked the ball into space for Messi to send a low shot past keeper Toni Doblas.
Zaragoza's Leonardo Ponzio was shown a straight red card two minutes after the break when he appeared to catch Daniel Alves with a flailing arm before Messi took his tally to five in six league matches in the 66th.
Seydou Keita and Andres Iniesta had efforts on goal but the ball eventually fell to World Player of the Year Messi just inside the penal
