Schmidt Peterson Motorsports driver James Hinchcliffe set the fastest time at the end of almost nine hours of IndyCar testing on Tuesday on the Sebring short layout.
Ahead of IndyCar's open test at new-for-2019 venue Austin next month, five IndyCar teams used up one of their allocated testing days at Sebring.
Hinchcliffe, who won last year's Iowa race in a difficult campaign, finished the day 0.09 seconds clear of Andretti Autosport's Zach Veach.
Rahal Letterman Lanigan Racing's Takuma Sato prevented a three-car Andretti train by slotting into third ahead of Ryan Hunter-Reay and 2018 title contender Alexander Rossi.
Ex-Ganassi driver Ed Jones had his first experience of his new team, driving for a partnership between Scuderia Corsa and Ed Carpenter Racing, and finished sixth overall.
His 2019 Chip Ganassi Racing replacement, Felix Rosenqvist, was 0.12s slower and ended his day in seventh.
Hinchcliffe's ex-Formula 1 driver new team-mate Marcus Ericsson returned to the scene of his first IndyCar test and mustered eighth.
SPM's general manager Taylor Kiel said he was satisfied with the work from both of his drivers.
"James was quickest in the morning and the afternoon, so it was a good day," he told Autosport.
"We did around 80 laps with James and focused on validating a lot of the work we'd done in the off-season, which was improving on a couple of areas where we struggled last year.
"There were times when we could be quick but weren't consistent with it.
"So we've taken big swings at a couple of things to make a more predictable package and one that stays consistent on race day."
Ericsson managed around 120 laps, and Kiel said changing conditions at Sebring were a "totally different challenge" for the Swede.
"Typical Sebring - a completely different track than we saw last month!" said Kiel.
"It was starting from square one for Marcus in terms of car set-up.
"But that's not a bad thing, because it's important to us that he is totally comfortable in the car whatever the conditions.
"We want him to know what particular changes to the car will do and therefore what to ask for when we get to St. Pete, or Long Beach or Barber.
"So we did what we did at his first test - set up a straightforward test plan with a lot of big-ticket items that we wanted him to feel."
Hunter-Reay's race engineer Ray Gosselin - who has been linked to a role with McLaren's Indianapolis 500 entry - said it was too early to draw an idea of the competitive image.
"But whatever you've worked on in the off-season, whether it's tyre longevity or riding the bumps better, you still don't know where you stand compared with the others until it counts," Gosselin told Autosport.
"We'll know a bit more when we get to the Laguna Seca test [February 8] and spring training at the Circuit of the Americas [February 12-13] in terms of all the teams' off-season gains."
Sebring test times
Rahal Letterman Lanigan
Rahal Letterman Lanigan
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