A Red Sox loss would've locked up playoff spots for the Tampa Bay Rays and New York Yankees. Instead, Boston took an early lead, pulled away and stayed mathematically in the wild-card race while the Rays and Yankees lost.
The magic number remains at one for the Rays and Yankees to reach the postseason.
David Ortiz, Victor Martinez and Adrian Beltre each drove in two runs. Marco Scutaro got three hits and scored three times as Boston won the opener of a four-game series.
Buchholz (17-7) pitched eight innings and scattered five hits, striking out five and walking one.
Buehrle (12-13) gave up 11 hits in six innings and lost his third straight decision.
The Red Sox took a 2-0 lead in the first when Martinez singled with two outs, Beltre doubled and Ortiz hit a two-run double.
Scutaro opened the third with a double and later scored on a sacrifice fly by Martinez.
The White Sox put runners on second and third with none out in the third but failed to score. Brent Morel lined out, Juan Pierre struck out and Omar Vizquel grounded to Buchholz, ending the inning.
Beltre's RBI single in the fifth made it 4-0. Morel drove in Chicago's run in the fifth with a deep sacrifice fly.
Three White Sox batters tagged Buchholz for deep flies in he seventh, all caught at the warning track.
Beltre doubled home Martinez in the ninth to extend the Red Sox lead to 6-1.
Martinez has a 12-game hitting streak.