The Penske driver, using a two-car draft, was able to break into the 198mph bracket reaching an average speed of 198.605 mph, with a lap time of 45.3126 seconds, the fastest seen during the three days of running. His Penske team-mate Kurt Busch was second, lapping in the same tenth and also reaching a similar speed while working in tandem with the Nationwide Series champion.
"It's a completely new breed of racing," said Keselowski about drafting on the new Daytona surface, which offers more grip.
"It will take an intelligent duo to pull it off. From a driver's side, it's similar to a baton relay. If you have the two fastest runners in the world and you put them in a baton relay and they can't exchange, an average Joe that can exchange will beat them.
"As the weekend has progressed, it has become more and more obvious, the thought of there being a big pack - I think we might see an extinction of that here."
The Joe Gibbs Racing duo of Joey Logano and Denny Hamlin had been fastest in the morning, lapping over 197mph, while Richard Petty's AJ Allmendinger became the first Ford driver to test in the draft, working with rookie Steven Wallace to set the fifth and sixth fastest laps of the morning session.
Despite drafting speeds reaching almost 200mph, NASCAR officials did not anticipate any changes being made to the current restrictor plate, which uses holes of 29/32nds of an inch.
Drivers making single-car runs, which continued to be a clear majority, lapped in the 185mph bracket, topped by Roush Fenway's Greg Biffle on Saturday afternoon and followed by the Earnhardt Ganassi duo of Jamie McMurray and Juan Pablo Montoya.
Sprint Cup director John Darby underlined that many teams focused on testing the two-car breakaway, which some still doubt will yield as much dividend as it has shown in the past at Talladega come race day.
"Obviously the guys are working on the tandem deal knowing that's faster than the draft," Darby said. "Everybody's working on a little different agenda, and it's all trying to find that edge to win the Daytona 500.
"I think this test has done more in building confidence. There's always some anxiety around what happens when a track repaves."
Teams will return to Daytona in the second week of February for the Budweiser Shootout, followed by the Daytona 500 a week later.
Bowyer leads first Daytona testHammers lead Barrera chase
