The cooler, overcast afternoon proved to be better for grip than the morning session and everyone but Andretti Autosport team mates Marco Andretti and James Hinchcliffe improved their time in the final session, with Marco's best time coming on Tuesday morning.
"We're definitely going to be gambling a little bit on setup because we've tried a bunch of different concepts," explained Marco. "So now, it is all about picking the right one to roll off there [at St. Petersburg]. We have to picture the types of corners on this track that replicate over there and hopefully go with the right one. On the Chevy side, it is all good."
Meanwhile Hinchcliffe was the only driver not to improve his time from day 1 of the two-day test. During the Tuesday morning session, Hinchcliffe ran off the track just before lunch and executed a pirouette that sent out clouds of dirt into the air, although no harm was done to car or driver.
"We learned what things don't work, so now we'll work on the other things to pull everything together to find the speed we're missing" said Hinchcliffe, insisting that even a lack of progress was positive at this stage.
HVM finally got some decent running in, after losing most of Monday to an electrical gremlins with the Lotus engine which persisted into Tuesday morning. But eventually Simona de Silvestro was able to run 64 laps and post a time of 53.2312s for the test, just over a second off the lead time set by Castroneves.
"Better day today but still needs lots of improvement!" de Silvestro tweeted at the close of the session. "We will get there!"
Wednesday sees Sebring handed over to the Firestone Indy Lights team for their pre-season test session, before the second block of IndyCar teams arrive for their turn on track on Thursday and Friday.
The cars running at the end of the week include JR Hildebrand (Panther-Chevrolet), EJ Viso, Tony Kanaan and Rubens Barrichello (KV Racing Technology-Cheverolet), Scot Dixon, Dario Franchitti, Graham Rahal and Charlie Kimball (Ganassi-Honda), Mike Conway (AJ Foyt-Honda), Takuma Sato (Rahal Letterman Lanigan-Honda), Ed Carpenter (Ed Carpenter Racing-Chevrolet), Oriol Servia (Lotus Dreyer & Reinbold Racing), Josef Newgarden (Sarah Fisher Hartman Racing-Honda), Alex Tagliani (Bryan Herta Autosport-Honda) and - engine availability permitting - Sebastien Bourdais and Katherine Legge of Lotus Dragon Racing.
Will Power wasn't sure how comparable the times later this week will be with those set on Monday and Tuesday.
"Oh, that is right, I forgot about that - Ganassi will be here Thursday," he said when asked. "It is so hard to tell this track, to be honest. It is a very strange circuit for testing, because I don't think there is any place we go that is like it."
Sebring day 2 testing times