Busch, attempting to become the first driver to sweep Cup and Nationwide events on back-to-back weekends since Harry Gant in 1991, led 151 of 200 laps. After he took the lead for the first time on the Lap 22, Busch surrendered it only during pit stops, most that were done under green.
The race's fourth and final caution brought Jimmie Johnson, winner of four of the previous seven Cup races at Fontana, into play, lining him up on the front row with Busch for a restart with nine laps to go. Kevin Harvick was farther back, the outside of the third row.
Busch's Toyota handled Johnson's Chevrolet on the restart, but Johnson closed up with five laps to go and passed Busch with two-and-a-half to go. Busch faded and Harvick charged past him, catching Johnson on the back straight on the final lap. Harvick put his Chevrolet's front bumper into Johnson's rear bumper, loosened him up entering Turn Three and passed him for the lead in Turn Four. The only lap Harvick led all day won the race, his first in 39 combined Cup (18), Nationwide (17) and Camping World Truck Series (four) races at the track.
The thrilling conclusion takes us to five things we learned in the Auto Club 400.
1. Harvick re-established himself as a favorite to win the championship.
This was a significant victory in Harvick's career far beyond the fact it was the first on his home track. Harvick, from Bakersfield, Calif., managed to beat Johnson in a head-to-head matchup on one of the five-time champion's best tracks. Harvick finished second to Johnson in Fontana's early-season race last year, hitting the wall late.
"We had them all beat last year and I gave it away," Harvick said.
Harvick also showed his resiliency. He was regarded as a favorite in the Daytona 500, but early engine failure opened his season with a 42nd-place finish. Harvick was fourth at Phoenix and eighth at Bristol to rise to 15th in the points. He's up to ninth now and certain to keep climbing.
"We have just had a lot of adversity that we fought through," Harvick said. "We knew our cars were fast enough to win races. We just haven't had the circumstances to right. Today, we had a fast car and the circumstances to right."
Harvick made this circumstance happen. "I knew if I was going to hit the wall, it wasn't going to be 'til Turn Four coming to the checkered," he explained. "It was tight, but it was the right time to go. I really had a good run coming off of Turn Two and he (Johnson) rolled up in front of me, so I just laid on the back bumper all the way down the back straightaway, give him a couple of seconds to think about what was going to happen going into Turn Three.
"The reason I did that, I just needed the one lane up top. I knew what I was gong to do. I was hoping he would just roll through the middle of the racetrack or on the bottom or something. So, it all worked out."
Score round one of Harvick vs. Johnson for Harvick. It will be a rivalry to watch the rest of the season.
2. Joe Gibbs Racing has serious engine problems.
Denny Hamlin started on the front row, but said his Joe Gibbs Racing-built Toyota engine began losing power early and a "valve train" failure eliminated him just past the halfway point, leaving him to finish 39th. It was the fourth blown engine for the team this season. Joey Logano lost one at Phoenix and another had to be replaced before Sunday's race, forcing Logano to start at the back. Busch also had an engine failure at Las Vegas.
In addition, the team had an engine blow up that caused a fire when it was on the dynamometer at its shop on Feb. 4.
"We definitely got to go to work and get the reliability down," Hamlin said.
3. Dale Earnhardt Jr. is laying the groundwork for a Chase season.
Earnhardt has been steady and he likes it. Five races into his partnership with crew chief Steve Letarte, he's finished between eighth and 12th four times and is 12th in overall points. On Sunday, Earnhardt was 12th at Fontana and notched the type of result that could form the foundation of a Chase season.
"We're a top-10 team," Earnhardt said. "We're doing pretty good. I like the consistency. That's something I've never really had. This is the most consistent I've ever been in my whole career, so that's a good thing. Steve (Letarte) and the team get all the credit for how well the cars drive and how well they improve throughout the race. He was able to improve the car throughout the race and make the adjustments that we needed to get us up there."
Earnhardt's description of what's happening is the exact opposite of last year under crew chief Lance McGrew. Earnhardt often started the race strong, but lost ground in the second half.
4. Brian Vickers is mounting a promising comeback season.
Vickers, who missed most of last season with serious health issues, finished a season-best eighth. He also was 10th at Las Vegas, pointing to the No. 83 Toyota team having a strong intermediate track package. Vickers isn't likely to be a Chase contender, but he seems headed for some strong performances that will move his career forward.
"We want to win, but I think everyone is pretty happy (with eighth)," Vickers said. "This is what the 83 Red Bull team needed, a good, solid day."
5. Casey Mears, Germain Racing crack top-35 in owner's points.
The top-35 in owner's points that guarantee a starting position in Cup races reset from the 2010 season to 2011 with the sixth race next week at Martinsville. For the smaller teams, it's a major goal, a sales pitch to sponsors and the ability to work on preparing cars for the race rather than qualifying. It's how teams get better.
Germain Racing's No. 13 with Mears is 35th, ahead of TRG's Andy Lally, TRG's Dave Blaney and Front Row Motorsports' Travis Kvapil, among others. Mears didn't make the Daytona 500, but has qualified for four straight races. He finished 18th at Phoenix, 25th at Las Vegas, 37th at Bristol and 29th at Fontana.
Germain has an 18-race sponsorship deal with Geico and is hoping to find the funding to run the entire season. Missing Daytona was a blow to the team, which couldn't afford to miss any more races. With fewer cars attempting to qualify -- nobody went home from Fontana -- it's becoming easier to make the races, but nothing is better than knowing you're going somewhere to race.