In 2008, Hornish drove full-time for Penske in its renumbered No. 77 car. Before the season, Penske swapped cars and owners' points with Kurt Busch; Hornish was guaranteed a starting position in the first five races and Busch, who won the series championship in 2004, would also be guaranteed a starting position as the most recent series champion driving a car outside the top 35 in owners' points. At the season-opening Daytona 500, Hornish qualified in 19th place; he finished 15th as teammates Ryan Newman and Busch were first and second, respectively. In the season's second race, the Auto Club 500 at Auto Club Speedway, Hornish sustained collateral damage when Casey Mears crashed into Dale Earnhardt Jr. on lap 22. Mears' car flipped 270 degrees, and Hornish's car caught fire. Hornish finished in 43rd place. Although he struggled during his rookie season, he drove well in May at Lowe's Motor Speedway. In the exhibition Sprint Showdown at Lowe's, Hornish started eighth and finished second. By finishing in the top two, he qualified for the exhibition 2008 NASCAR Sprint All-Star Race, starting 23rd out of 24 cars and finishing seventh. Hornish had his best finish (13th place) of the season at the Coca-Cola 600, also at Lowe's. Late in the season his Penske team dropped out of the top 35 in owners' points, and Hornish failed to qualify for the AMP Energy 500 at Talladega Superspeedway and the season-ending Ford 400 at Homestead-Miami Speedway. He finished 35th in the drivers' standings, with 2,523 points. Hornish was second in the rookie of the year standings, after a season-long battle with Regan Smith.