Dilshan equaled his career-best score with an unbeaten 160, his 11th century in 230 ODIs and first in a year, while Sangakkara made a quickfire 105 to register the 13th century of his career.
Sent into bat, Dilshan anchored Sri Lanka`s innings and hit 11 fours and three huge sixes during his 165-ball unbeaten stay.
Sangakkara, on the other hand, was at his destructive best, piling up his 105 runs off just 87 balls with eight boundaries and two huge hits over the fence.
Dilshan and Sangakkara got together after the 12th over and maneuvered the score till the 44th over, putting together exactly 200 runs for the second wicket, the biggest stand of the series so far.
In with an outside chance to book a place in the best of three final of the series, Mahendra Singh Dhoni had no hestitation in bowling first after winning the toss today, as India needed to chase down Sri Lanka`s target inside 40 overs to avail a bonus point and stay afloat in the competition.
The Lankans got off to a decent start with captain Mahela Jayawardene and Dilshan putting together 49 runs for the first wicket before the former was holed out by Virender Sehwag atn the slip off Ravindra Jadeja.
The dismissal forced Dilshan and new man Sangakkara to slow down as they raised their scores mostly in ones and twos with occasional hits in between to raise up the team`s 100 in the 22nd over.
Dilshan was the first one to reach his half century, hitting five fours off 68 balls. Sangakkara followed suit and reached the landmark in 55 balls.
With their eyes firmly set, the duo then stepped up the tempo and claimed the batting powerplay after 32 overs with Sri Lanka`s score reading 150 for two. The batting powerplay yielded 41 runs for the islanders.
Dilshan was the first one to reach his century when he pushed Jadeja through mid-on and claimed a single in the 41st over.
Two overs later, it was Sangakkara`s turn to raise his bat when top-edged Zaheer through point and third man to pick up two runs.
But soon after scoring his ton, Sangakkara departed in the 44th over, trying to smash Praveen Kumar on the onside but missing it completely to be out bowled.
India built on this success when they ran out Thisara Perera (3) in the 46th over. But the wickets failed to put a brake on Dilshan, who did not spare a single Indian bowler, to pile up the team`s 300 in the 48th over.
India`s bowling and fielding both looked listless and the visitors didn`t look like a side who were desperate to win the game with a bonus point.
The Indian bowling attack -- both pacers as well as spinners -- looked ordinary against the determined Sri Lankan batsmen.
Zaheer (1/61), Praveen (1/64) and Jadeja (1/43) shared three wickets between them, while other dismissal came in the form of run out.