Scotland's Dario Franchitti leads the standings going into Sunday's final event as he seeks a third consecutive IndyCar season title.
The 38-year-old from Bathgate is 18 points clear of Will Power ahead of the 200-lap finale in Las Vegas.
The rivals were embroiled in a similar winner-takes-all clash last year, with Franchitti overhauling the Australian.
"For me, the most important thing you can have is that desire to win," Franchitti told BBC Radio Scotland.
"My drive to be successful is still as strong as it ever was and that can make the difference between giving 99% and 100%."
Franchitti is aiming for a fourth season title in five years, missing out only in 2008 for an ill-fated move to US stock cars.
The late Jim Clark won two Formula 1 championships, while Sir Jackie Stewart triumphed three times but Franchitti is quick to dismiss the notion that his achievements in the United States could eclipse those of his fellow Scots.
"If I won another 10 championships, I would still feel very much in the shadow of Jim Clark and Jackie Stewart. They, for me, were on a completely different level. Formula 1 is the pinnacle of our sport.
"I would also put [former world rally champion] Colin McRae in their company - they are three of the greatest drivers the world has ever produced."
Franchitti has won four of the 17 events this season, while Power has taken the chequered flag on six occasions.
"I've achieved more than I thought I ever would," added Franchitti, the older cousin of F1 driver Paul di Resta. "Everything else is just a bonus."