Jamie Whincup

Jamie Whincup in action at Phillip Island.

The most unpredictable season in Australian touring car racing history will end with the tightest title showdown ever in next weekend's Sydney 500.

The V8 Supercars championship has come down to a fight between the year's best three drivers in two 250km encounters on the bruising Sydney Olympic Park street circuit, which will host a new twilight race on Saturday.

The title-contending trio is defending V8 champion Jamie Whincup, his veteran teammate Craig Lowndes and Bathurst 1000 winner Mark Winterbottom, who are covered by just 124 points.

Jamie Whincup.

Leader: Jamie Whincup is 20 points ahead. Photo: Getty Images

With a maximum 300 points available, the final race on Sunday will almost certainly be the championship decider - and the conclusion just as likely to be dramatic given the Sydney 500's four-year history of incidents and upsets.

Whincup leads Lowndes by 20 points. While Winterbottom is close enough to be a threat, the reality is that the points gap is too far to bridge unless Whincup and Lowndes both score very poorly or fail to finish races.

There is, in fact, a fourth contender for the title, but Will Davison's chances are only mathematical as he is 223 points off the lead. It would take catastrophes for the top three to bring Davison into realistic calculation.

Whether it's a two- or three-way tussle, the title will be decided in the closest finish in the 53-year history of the Australian touring car championship and its modern successor, the V8 Supercars championship.

It is fitting that the series will finish on a knife edge as it has been the most unpredictable ever, with the most different race-winners in a single season.

The change to the new-generation V8 racers not only ended nearly two decades of Ford/Holden duopoly, attracting new Nissan and Mercedes-Benz entries, but the technical upheaval levelled the competition between the top teams and the middle-order squads.

There have been 13 different winners (17 if you count the non-regular endurance race co-drivers) from eight teams in 34 races.

Whincup is bidding for a record-equalling fifth V8 crown, matching the feats of legends Dick Johnson, Mark Skaife and the late Ian Geoghegan.

Lowndes is trying to end the long wait for his fourth title after four near misses since 1999, while Winterbottom isn't giving up on his outside chance to claim his maiden V8 championship.

''There's not much pressure on me,'' Winterbottom said. ''I can go there and just go all out. I don't have to protect points. I can just go and have a big crack and dive into gaps, and just have a really good go, which is what I'm going to do.''