Oklahoma City made eight of its first 10 3-point attempts in the second half and never trailed after scoring the final five points before halftime.
Serge Ibaka chipped in 15 points and 10 rebounds and Kevin Martin had 16 points off the bench for the Thunder, who haven't lost consecutive home games since dropping two of the first three to start the 2010-11 season.
Nick Young led Philadelphia with 21 points, and Jrue Holiday had 15 points and nine assists. The Sixers fell to 2-5 on their eight-game road trip, which started before Christmas and concludes Saturday night at San Antonio.
Oklahoma City went 23 for 36 from the field, connecting at a sizzling 64 percent clip, while outscoring Philadelphia 63-43 in the second half.
The Thunder lost to Brooklyn at home on Wednesday night, clawing back from a 23-point deficit to tie it in the fourth quarter before falling 110-93.
On Friday, the Thunder opened their first double-digit lead shortly after coach Scott Brooks came walking out on to the court to call timeout, screaming, "Let's Go!" at his players after Westbrook had turned the ball over by driving into the back of teammate Kendrick Perkins shortly after halftime.
Neither player made an attempt to run to the opposite end of the court, and Jason Richardson threw down a two-handed slam off Holiday's alley-oop.
Durant came out of the timeout and immediately drove into the lane, kicking the ball out to Thabo Sefolosha for a 3-pointer, and then drilled a 3 on the next trip down for a 56-46 advantage. Richardson answered with a 3-pointer, a layup and a runner for the Sixers before Westbrook scored six points during an 8-0 burst that pushed the lead to 69-57 for Oklahoma City with 3:50 left in the third quarter.
The Thunder salted it away with a 16-3 run late in the fourth quarter, as both teams started filtering reserves onto the court.
Dorell Wright had 11 points and Thaddeus Young scored for Philadelphia. Spencer Hawes pulled down 13 rebounds.
After a tight first half that featured 14 lead changes, Oklahoma City scored the final five points of the first half to take a 46-42 lead and stayed in front the rest of the way.
Notes: Before the game, Sixers coach Doug Collins offered his analysis of the Thunder's offseason deal that sent Sixth Man of the Year James Harden to Houston for Kevin Martin. "I think where you're going to see the value of James Harden is come playoff time. That's when," Collins said. "Because James Harden in so many instances, was their point guard and Westbrook scored and Durant. I think that's when you'll really see because in the playoffs, you need as many playmakers as possible. Kevin Martin can really score that ball but he plays off other guys. I think people don't realize James Harden also last year made more free throws in the fourth quarter than anybody in the NBA." ... Oklahoma City plays 11 of its next 13 games on the road. After finishing its road trip at San Antonio on Saturday night, Philadelphia plays 13 of its next 15 games at home. ... Country star Vince Gill watched the game from a courtside seat along the baseline.