From 1979 to 1981, Unser raced in the CART series for Team Penske. Roger Penske wanted a proven winner to join his young driver Rick Mears. Unser won six times to Mears' three wins but Mears won the championship and Indy 500. In 1980 he became the first driver to win the California 500 four times. Unser won four times in 1980 and finished second in the season championship to Johnny Rutherford. His career ended in 1981 following a controversial win at Indianapolis.