For 2008, Carpenter returned with Vision Racing to drive the No. 20 Dallara-Honda. At the season-opening Gainsco Auto Insurance Indy 300 at Homestead, Carpenter qualified in 2nd place, but his time was nullified as his car – as well as the car of teammate A. J. Foyt IV – failed technical inspection. Despite starting at the rear, Carpenter worked his way through the order to finish in 6th place. Carpenter added another 6th-place finish at the Indy Japan 300 at Twin Ring Motegi. At the Indianapolis 500, Carpenter qualified in 10th place and finished in 5th place, leading 3 laps. After eight races, Carpenter ranked eighth in points, however, Carpenter only achieved top ten finishes in the Firestone Indy 200 at Nashville and the Meijer Indy 300 at Kentucky. Carpenter finished out the year with a fiery crash in the Peak Antifreeze Indy 300 at Chicagoland while running in the top five. Carpenter finished the season ranked in 15th place, with 320 points.