Stewart - who had previously won in Los Angeles, Houston and Phoenix - rode the perfect race after acing the holeshot around the first corner of the open-air AtandT Park stadium. He was able to pull away and beat Reed by almost five seconds by the chequered flag. The main event was the seventh to be held in the picturesque city and was the third victory for Yamaha.
"I'm starting to feel like my old self and I've just been training as hard as I can. Right now it's showing, and we'll see what happens. It has definitely been better the last couple of weeks than in weeks past, so we'll see what happens," said Stewart who increased his career win haul to 29. "We're going to Anaheim soon and we're just going to have to try to keep it going. We're still six points back and there's still a long way to go."
Joe Gibbs Racing's Josh Grant maintained his 100% record of top five positions in each event. The 2009 rookie is having an impressive campaign to-date and added 4th place in San Francisco to his tally of 1st, 3rd, 5th and 5th. Grant is third in the table, seven points behind his brand-mate.
Stewart will be looking to gain further points over Reed and possibly seize control of the championship for the first time this year at Anaheim (for the third and final visit) in Los Angeles next weekend.