In the 1985 Indianapolis 500, he was passed for the lead by Danny Sullivan in Turn One on lap 20. Immediately after completing the pass, Sullivan spun in front of Andretti. A caution flag for the spin minimized the time Sullivan would lose to Andretti by pitting to replace his tires. Sullivan took the lead for good 20 laps later when he passed Andretti without incident. Andretti dominated the 1987 Indianapolis 500, leading 170 of the first 177 laps of the race. His lead was so large, that he was advised to slow his pace to preserve his equipment. In a cruel twist of fate, when Andretti started running slower, his reduced engine rpm's created a harmonic imbalance in his turbocharged Ilmor/Chevrolet V8 that led to a broken valve spring with 20 laps to go.