The Colombian set the pace at the wheel of his Earnhardt Ganassi Racing Chevrolet with a lap of 29.036 seconds at an average speed of 185.976 mph, posted in the morning when the track temperature was at its coolest of the day.
Teams experimented with what is expected to be the new aero package for the majority of tracks, all running the new rear spoiler and left-side deck lid and window fins, aimed at keeping cars from getting airborne.
According to NASCAR's vice president of competition, Robin Pemberton, teams were allowed to play with the length of the deck lid, starting with a minimum of 17 inches, while the dimensions on the shark fin on the rear window and the spoiler are fixed.
The squads on track also tested with different gearing, running shorter ratios in the afternoon to try to compensate the loss of rpm coming from the increased drag generated by the new spoiler.
Richard Petty's Paul Menard topped the afternoon session in his #98 Ford, followed by Montoya, Stewart Haas's Ryan Newman, EGR's Jamie McMurray and reigning champion Jimmie Johnson.
Consensus in the Cup garage seemed to point at the new aero package not causing a major shift in the car's balance and handling, the same conclusion as drawn from the first test that some teams carried out at Texas a few weeks ago.
"It was good to know and put out of my mind that the spoiler was going to be a drastic difference in the way the car drives," said points' leader Kevin Harvick. "That is not the case. The car has a lot of grip with the tyre combination and the spoiler, so it drives really good.
"We went right to work on the things that we needed to because we felt comfortable with the car. I think that's been good and everything has gone well so far."
Jeff Gordon, who was never a big fan of the rear wing, didn't find a very different feel in the car on the track today, although he pointed out the big technical differences that the spoiler brings relative to the wing.
"Based on things we saw in the test, in our data that we have gathered, we thought the cars would drive pretty good and not be that much different and that is pretty much what we felt," said Gordon. "The cars don't have as much side force with the spoiler, so we've started getting into, for the last several years, is downforce, drag and then side force. You see skewing the cars.
"What we learned with the wing is that by running the car sideways as it entered the corner, that side force made up for even some of the drag and downforce that it took away. So now, we still have a lot of those things, but with the spoiler we just noticed where we lost a little bit of that side force but yet we have made up for it on total downforce on the car."
NASCAR officials also announced the aero and restrictor plate package for superspeedways, with spoilers set at 4.5 inches high without the higher side-extensions tested at Talladega. It will be 63 inches wide and have the same 70-degree angle at other tracks. A smaller restrictor-plate that those tested last week will be implemented for Talladega and Daytona, with holes measuring 30/32nds of an inch.
Teams will continue to test at Charlotte Motor Speedway on Wednesday before the new device makes its race debut next weekend at Martinsville.
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