Burton set a fastest lap of 28.539 seconds at an average speed of 189.215 mph, edging Harvick by more than two tenths of a second. Tuesday's pacesetter Juan Pablo Montoya was third in his Earnhardt Ganassi Chevrolet, the last driver able to lap under the 29-second bracket during the whole test.
All the fastest times were recorded in the morning session with cool track temperatures and the asphalt already rubbered in from the first day of running. The afternoon session, which was paced by Richard Petty's AJ Allmendinger, proved to be slower as the track became slick due to warmer conditions.
Reigning champion Jimmie Johnson, who was second fastest in the final session, said his Hendrick team was still hunting for the 'magic setting' for the new aero package and believes there may be increasing gaps between teams in the early races with the spoiler, although he expects everyone to catch up during the season.
"We might not be the first team to find the magic the spoiler wants, but we're usually pretty good at finding stuff in a hurry, and then the fact that it's a new element to the car brings a few months' worth of opportunity, I think," said Johnson.
"We saw that with the wing coming along, and truthfully the competition that was really, really equal before the wing has now gone away. I mean, the start of any rule change you have your largest separation, and then as time goes on, the teams that are behind catch up."
Nationwide Series regular Justin Allgaier, testing for Penske Racing, caused the only notable incident of the day when he hit the wall.
Teams will race the spoiler for the first time next weekend at Martinsville.
Alvarez takes Sevilla reinsBurton leads second spoiler test
