The PEAK Antifreeze & Motor Oil Indy 300 this weekend is the 15th of 17 events on the schedule, with Team Penske's Ryan Briscoe entering the 200-lap race with a four-point advantage over Dario Franchitti. His Target Chip Ganassi Racing teammate, Scott Dixon, is 20 points out of the lead.

It's the 12th time in 14 races that the margin between first and second has been 10 points or fewer, and the difference between first and third is the third-closest with three races remaining.

"The points championship looks like it's going to go down to the wire again, which we've been fortunate to have the championship do that for the last several years," Indy Racing League president of competition and operations Brian Barnhart said. "The contenders all have had issues to contend with early in the season, missed out on opportunities to score some important points. That's clearly something they have to avoid in the final races. You can't have any missteps from here on out; there just isn't any time to make that up."

The top three in points all have had success on the circuit. Dixon has been involved in the past two years that decided the title - 2008 fell in his favor. In '07, pole sitter Franchitti's pass of Dixon in Turn 4 of the final lap gave him the championship in the winner-take-all race.

"I think between the two of us we've got cars in the Target team that can win all those last three races," said Dixon, who has four second-place finishes (including the past three years in a row). "That's the attitude. We have to go out there and try and dominate and hopefully I'll win another championship."

Briscoe was the pole sitter last year and finished third behind Dixon and teammate Helio Castroneves.

"Looking at how this championship's gone so far, no one can hang on to the lead," said Briscoe, who has been the points leader five different times following the 14 races. "I think we're seeing that wins reward greatly, and I think whoever's going to win this championship needs to go out and win races. Obviously you need to finish and collect points. But getting those 50 points is always really important."

A look at Chicagoland Speedway's influence in the IndyCar Series championship:

·        2008: Helio Castroneves entered the 200-lap race trailing Dixon by 43 points. Worse, he was starting from the rear of the 28-car field because of a post-qualifying technical inspection infraction. But the Team Penske driver blazed a path to the front to beat Dixon to the checkered flag by 0.0033 of a second - the second-closest finish in IndyCar Series history. The runner-up finish enabled Dixon to win the title by 17 points.

·        2007: It was more final-lap drama when Dixon and Franchitti - on rival teams at the time - were wheel to wheel through Turn 2 with the championship going to the car that crossed the finish line first. Franchitti, who had trailed the past six laps, overtook Dixon's fuel-starved car in Turn 4 and went on to the race victory by 1.8 seconds and championship by 13 points.

·        2006: Four drivers entered the season finale with a shot at winning the title, which wasn't decided until after the checkered flag fell. Castroneves led Team Penske teammate Sam Hornish Jr. by one point, while '05 series champion Dan Wheldon was 18 points back and Dixon was 21 behind. Wheldon finished 0.1897 of a second ahead of Dixon, followed by Hornish and Castroneves. Wheldon and Hornish tied in points, with Castroneves two back and Dixon 13 off the pace. Hornish claimed his third series title based on the first tiebreaker (four wins to Wheldon's two).

·        2005: Wheldon opened a 102-point lead over Andretti Green Racing teammate Tony Kanaan with a victory in the 15th of 17 races, which allowed him to clinch the title in the next race. Wheldon, who won a series-record six races, led 88 of the 200 laps.

·        2004: Kanaan, who would go on to complete every lap during the season, finished third to Adrian Fernandez and Bryan Herta. The result gave Kanaan a 75-point margin over rookie teammate Wheldon with two races remaining. Kanaan wrapped up the title in the next race.

·        2003: Hornish won the race by 0.0099 of a second over Dixon to remain in championship contention, but it was Dixon's result that closed the gap on Castroneves with two races remaining. Castroneves, who won the previous race at Nazareth Speedway for a 25-point lead, retired with 17 laps left with a gearbox issue and finished 20th. Dixon gained 13 points on the front-runner and clinched the title with another runner-up finish in the season finale.

·        2002: Eight points separated Castroneves, Gil de Ferran and Hornish heading into the 14th race of the season. Hornish took charge of the championship with victories at Chicagoland and Texas by a combined margin of 0.012 of a second to edge Castroneves for the title by 20 points. At Chicagoland Speedway, Hornish dueled with Al Unser Jr. the final 50 laps and won by 0.0024 of a second - the closest finish in IndyCar Series history.

·        2001: In the 12th of 13 races on the calendar, Hornish wraps up the championship with a second-place finish to Jaques Lazier.