After his retirement, Mears assumed a mentor role at Team Penske. Mears' ability to analyze and evaluate racing techniques in real-time, whether as a driver or while advising younger drivers, has left a lasting legacy on the INDYCAR paddock.

Among the various Team Penske drivers Mears mentored, he played a vital role as spotter for Helio Castroneves' three Indianapolis 500 victories in 2001, 2002, and 2009. Castroneves credited Mears' mentorship as a crucial component in his learning and understanding of the Indianapolis Motor Speedway. In 2009, Castroneves qualified on pole position and twice led the race for 66 laps, including the final 58. He crossed the finish line just under two seconds ahead of second-place finisher Dan Wheldon. With that victory, Castroneves became the first Brazilian driver to win the race three times.