LAS VEGAS -- Dale Earnhardt Jr. knew he probably didn't have enough fuel to finish. Being in Vegas, he decided to gamble anyway.
And when Earnhardt's tank went bust on the final lap, Brad Keselowski was right there to clean up.
Keselowski surged ahead when Earnhardt ran out of fuel, claiming a dramatic victory Sunday in the NASCAR race at Las Vegas Motor Speedway.
Earnhardt's Chevy sputtered and slowed out of the second turn, and Keselowski roared past him on the backstretch in his Penske Ford for the first weekend sweep in his career. Keselowski followed up Saturday's Nationwide Series victory with his first Las Vegas Cup win, doing it in exhilarating fashion against the friend and mentor who gave him his first big break in racing.
"That's what you live for as a driver, at least I do," Keselowski said. "Those moments where you're side by side, and you lay it all out on the racetrack and bring back the car with the tires smoking, engine smoking, and you're worn out inside because you gave it all you had. It was one of those races there at the end."
Keselowski knew all about the fuel shortage faced by Earnhardt and Carl Edwards, who both made their final pit stops about 10 laps before him. So Keselowski decided to force the issue, getting around Edwards and pushing for the lead so Earnhardt would be forced to abandon his conservative, fuel-saving lines.
"I felt like we could run him down," Keselowski said about the driver who put him in his first Nationwide ride. "He was going to have to burn fuel to keep me behind him. At that point, it was just a matter of whether a yellow (flag) came out or not, because it was just a ticking time bomb. It worked in our favor today."
Earnhardt finished second and didn't regret it, secure in his overall position thanks to the new rules in the Chase for the Sprint Cup championship, which puts increased emphasis on wins. Still, Earnhardt and his Hendrick Motorsports ride were just a few ounces of fuel shy of earning their second victory in three races to start the season.
When Earnhardt sat down for his post-race news conference in front of two cans of his sponsor's energy drink, he picked up one can wistfully: "That's all we needed, just 16 ounces."
The Daytona 500 champion was disappointed, but not discouraged after his spectacular start to the NASCAR season. He also finished second last week at Phoenix.
"We weren't supposed to make it," Earnhardt said. "We were trying to save as much as we can and make it work, but we knew we were short. We wouldn't have finished second if we didn't have that strategy."
Earnhardt did become just the fifth driver in the modern era (since 1972) to start a season with three consecutive top-two finishes. Three of the previous four went on to win the championship ( Jimmie Johnson in 2006, Cale Yarborough in 1977, Richard Petty in 1974; Dale Jarrett finished third in 1996).
Keselowski, the 2012 Sprint Cup champion, virtually assured himself of a spot in the Chase after missing it entirely last season.
"It's just such a reliever for everyone on the team to get that win in early, and be able to enjoy the races and opportunities that we have instead of being stressed out about them," Keselowski said. "You know, I think if anything it actually lends itself to better racing."
Earnhardt also praised NASCAR's new Chase setup, which allowed him to take a fuel gamble in Vegas after winning already this season. Additional wins are worth bonus points in the Chase, while a second-place finish doesn't help his position much -- hence the motivation to go for broke on an empty tank.
"I think the new format is definitely is showing it has tons of positives," Earnhardt said. "It's better as far as entertainment for our sport. It gives us freedom, and it's nice to have that freedom to do the things that we did today, even though we knew our odds weren't good. We really shouldn't have made it, and we didn't, but we got to try because of the new system."
With his wife due to give birth at any minute, Paul Menard finished third in his Richard Childress Racing Chevy in front of Keselowski's teammate, pole-sitter Joey Logano. Edwards was fifth in a Roush Fenway Racing Ford, and Earnhardt teammate Johnson came in sixth.
The Las Vegas race is the first of 11 on 1.5-mile tracks, and NASCAR spent much of the offseason working on ways to improve the racing on these tracks with a new aerodynamics package and other improvements. The changes resulted in 23 drivers breaking the track speed record during qualifying, but the racing wasn't particularly thrilling until that final lap.
Keselowski and Earnhardt are the only two drivers to finish in the top five in each of the season's first three races, and they dueled down the stretch after Earnhardt passed him for the lead on a restart with 42 laps to go. Earnhardt had gone to the pits on the 211th lap and attempted to stick it out.
Keselowski was in fine form after his third-place finish in Phoenix last week without crew chief Paul Wolfe, who had returned home for his child's birth. Keselowski also finished third at Daytona.
Keselowski is the second driver to win both Vegas races in the same weekend, joining Jeff Burton in 2000.
Information from The Associated Press and ESPN Stats & Information was used in this report.