Scott Dixon topped the first day of IndyCar's official pre-season test at Barber, out-pacing Simon Pagenaud with his final lap of the day.
Ganassi's Dixon led a Chevrolet engine and aero kit lockout of the top five places, with Andretti Autosport's Ryan Hunter-Reay the top Honda runner, nearly four tenths of a second back.
"I think both cars are very different," said Dixon. "I don't care what it looks like as long as it's fast.
"It's been a significant change in driveability or how to attack the car with all the downforce.
"We're working with the balance issues, just trying to feel out some of the changes with the aero kit and the loads changing significantly with the corner speeds."
Pagenaud set the pace in the morning session for Penske, which had all four of its cars in the top five at the end of the day, with Will Power ahead of Juan Pablo Montoya and Helio Castroneves.
2012 champion Hunter-Reay described the Honda aero kit, which was outpaced in testing at NOLA Motorsports Park last weekend as well, as "a work in progress".
"This is what testing and development is about," he added. "It's almost like you're starting with a new car.
"You feel when you're in the car that every lap is critical because you're one step closer to the season beginning."
IndyCar is also using this test to trial a new LED display that will show a car's race position, to make events easier to follow for fans at trackside.
The test continues on Tuesday, before the teams switch to private testing at Sebring and NOLA.
The test also marked confirmation of two more driver signings for 2015, with Carlos Huertas signing for a second season with Dale Coyne, and former Auto GP racer Franceso Dracone returning to IndyCar for the first time since 2010 in a four-race deal alongside him.
|1||Simon Pagenaud||Team Penske||Dallara/Chevrolet||1m07.7456s||-|
|2||Scott Dixon||Chip Ganassi Racing||Dallara/Chevrolet||1m08.0401s||0.2945s|
|3||Josef Newgarden||CFH Racing||Dallara/Chevrolet||1m08.2214s||0.4758s|
|4||Will Power||Team Penske||Dallara/Chevrolet||1m08.2600s||0.5144s|
|5||Helio Castroneves||Team Penske||Dallara/Chevrolet||1m08.3383s||0.5927s|
|6||Stefano Coletti||KV Racing Technology||Dallara/Chevrolet||1m08.4816s||0.7360s|
|7||Sebastien Bourdais||KVSH Racing||Dallara/Chevrolet||1m08.6508s||0.9052s|
|8||Graham Rahal||Rahal Letterman Lanigan||Dallara/Honda||1m08.6550s||0.9094s|
|9||Carlos Munoz||Andretti Autosport||Dallara/Honda||1m08.6637s||0.9181s|
|10||James Jakes||Schmidt Peterson Motorsports||Dallara/Honda||1m08.6761s||0.9305s|
|11||Tony Kanaan||Chip Ganassi Racing||Dallara/Chevrolet||1m08.6774s||0.9318s|
|12||Juan Pablo Montoya||Team Penske||Dallara/Chevrolet||1m08.7068s||0.9612s|
|13||Charlie Kimball||Chip Ganassi Racing||Dallara/Chevrolet||1m08.7630s||1.0174s|
|14||Takuma Sato||AJ Foyt Enterprises||Dallara/Honda||1m08.9856s||1.2400s|
|15||Marco Andretti||Andretti Autosport||Dallara/Honda||1m09.0165s||1.2709s|
|16||James Hinchcliffe||Schmidt Peterson Motorsports||Dallara/Honda||1m09.1466s||1.4010s|
|17||Luca Filippi||CFH Racing||Dallara/Chevrolet||1m09.6855s||1.9399s|
|18||Carlos Huertas||Dale Coyne Racing||Dallara/Honda||1m10.0365s||2.2909s|
|19||Gabby Chaves||Bryan Herta Autosport||Dallara/Honda||1m10.3056s||2.5600s|
|20||Sage Karam||Chip Ganassi Racing||Dallara/Chevrolet||1m10.7555s||3.0099s|
|21||Francesco Dracone||Dale Coyne Racing||Dallara/Honda||1m13.2615s||5.5159s|
|1||Scott Dixon||Chip Ganassi Racing||Dallara/Chevrolet||1m07.4805s||-|
|2||Simon Pagenaud||Team Penske||Dallara/Chevrolet||1m07.5329s||0.0524s|
|3||Will Power||Team Penske||Dallara/Chevrolet||1m07.5495s||0.0690s|
|4||Juan Pablo Montoya||Team Penske||Dallara/Chevrolet||1m07.6266s||0.1461s|
|5||Helio Castroneves||Team Penske||Dallara/Chevrolet||1m07.7703s||0.2898s|
|6||Ryan Hunter-Reay||Andretti Autosport||Dallara/Honda||1m07.8494s||0.3689s|
|7||Josef Newgarden||CFH Racing||Dallara/Chevrolet||1m07.8647s||0.3842s|
|8||James Hinchcliffe||Schmidt Peterson Motorsports||Dallara/Honda||1m07.8982s||0.4177s|
|9||Tony Kanaan||Chip Ganassi Racing||Dallara/Chevrolet||1m07.9079s||0.4274s|
|10||Graham Rahal||Rahal Letterman Lanigan||Dallara/Honda||1m07.9317s||0.4512s|
|11||Carlos Munoz||Andretti Autosport||Dallara/Honda||1m07.9540s||0.4735s|
|12||Charlie Kimball||Chip Ganassi Racing||Dallara/Chevrolet||1m07.9634s||0.4829s|
|13||Sebastien Bourdais||KVSH Racing||Dallara/Chevrolet||1m08.1515s||0.6710s|
|14||Stefano Coletti||KV Racing Technology||Dallara/Chevrolet||1m08.1848s||0.7043s|
|15||James Jakes||Schmidt Peterson Motorsports||Dallara/Honda||1m08.1940s||0.7135s|
|16||Marco Andretti||Andretti Autosport||Dallara/Honda||1m08.2657s||0.7852s|
|17||Takuma Sato||AJ Foyt Enterprises||Dallara/Honda||1m08.3626s||0.8821s|
|18||Luca Filippi||CFH Racing||Dallara/Chevrolet||1m08.3947s||0.9142s|
|19||Carlos Huertas||Dale Coyne Racing||Dallara/Honda||1m08.4797s||0.9992s|
|20||Jack Hawksworth||AJ Foyt Enterprises||Dallara/Honda||1m08.7414s||1.2609s|
|21||Gabby Chaves||Bryan Herta Autosport||Dallara/Honda||1m09.0013s||1.5208s|
|22||Francesco Dracone||Dale Coyne Racing||Dallara/Honda||1m11.9996s||4.5191s|