The champions tore apart Atletico Madrid 5-2 on Saturday with four first-half goals and Racing suffered similar treatment, conceding three in seven first-half minutes from Zlatan Ibrahimovic, Messi and Gerard Pique.
Messi added a fourth after the restart to take his tally to five from four league games before Oscar Serrano replied late for Racing.
Barcelona have 12 points from four games, three ahead of second-placed Real Madrid who visit Villarreal on Wednesday.
Worries that Ibrahimovic would take time to adapt after replacing Samuel Eto'o in Barca's attack now look misplaced as the Swede bagged his fourth goal in as many games.
Messi floated a cross to the back post for the Swedish striker to nod the opener in the 20th minute and almost immediately the former Inter Milan marksman powered into the area and hit the post with another effort.
Four minutes later Messi played a one-two with Xavi, wrong-footed a defender and curled a shot into the corner of the net from the edge of the box.
The game was over as a contest in the 27th when Ibrahimovic controlled a ball in the area. As five defenders swarmed around him, he back-heeled a pass to the unmarked Pique who slotted home the third.
Ibrahimovic was substituted after going over on his ankle in the second half before Messi added his second with a trademark run across the edge of the area and a shot inside the far post.
Earlier, Sevilla ended Real Mallorca's flying start to the season with a 2-0 win at the Sanchez Pizjuan.
The islanders started the day in fourth spot after two wins and a draw from their first three games but were undone by improving Sevilla, who could have won by an even bigger margin.
Sebastien Squillaci headed in a corner after 17 minutes and Jesus Navas set up Diego Perotti for a back-post header soon after to lift Sevilla to third with nine points from four games.
