Reutimann, a two-time winner in the series, set a fastest lap of 45.970 seconds, at an average speed of 195.780 mph, achieved while running in tandem with his MWR team-mate Truex, who was second on the timesheets.
Behind them, Red Bull's returnee Brian Vickers was third-fastest, also achieving his best lap while working in tandem with his team-mate Kasey Kahne.
Stewart Haas' Tony Stewart was fifth, setting his best lap while drafting in single file with both MWR and Red Bull cars in a five-car group, the biggest seen during the four-hour session. However, his best lap was over a second slower than what the top four managed after splitting into two-car team formations.
Despite much anticipation to the afternoon session, few drivers ventured on the track to draft and figure out the effect of the new, smoother Daytona asphalt, which proved to allow more bump-drafting than in the past.
"It looked like a lot of guys were just working on a lot of stuff today so maybe they're going to be focused on drafting tomorrow," said Vickers. "I'm sure before we leave you'll see a pretty big pack. I can't imagine you wouldn't because I know pretty much everybody wants to see how the cars react in that situation, the track and all that stuff."
Many drivers and teams continued to focus on single-car runs, hoping to get most of their programmes done before switching to drafting mode. Some rain is forecast for the Daytona area on Friday.
Teams will continue to test until Saturday for the Daytona 500, which takes place on February 20.
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