The 52nd International 500 Mile Sweepstakes was held at the Indianapolis Motor Speedway in Speedway, Indiana on Thursday May 30, 1968. For the second year in a row, one of Andy Granatelli's STP Turbine-powered machines was leading late in the race, but once again, it failed within sight of victory. On lap 174, Lloyd Ruby's engine misfired allowing Joe Leonard to take the lead in the Lotus 56 Turbine. Leonard, however, suffered a flameout on the lap 191 restart, and rolled to a silent and shocking halt. Bobby Unser in the venerable piston-powered Offenhauser, inherited the lead, and despite gear linkage trouble, won the first of his three Indy 500 victories (1968, 1975, 1981). This was the final Indianapolis 500 to feature a front-engined car in the starting field. Of the 33 cars, 32 were rear-engined machines (including three turbines). Jim Hurtubise's entry, which dropped out after only nine laps, was the last front-engine car to race in the 500. This was also the first 500 won by a turbocharged engine. During the month, film crews were on hand to film various action shots and stock footage of the race proceedings to be used in the 1969 film Winning, starring Paul Newman. With of precipitation in the Indianapolis area in May, the 1968 race featured the wettest month on record for the Indy 500. Rain hampered practice and qualifying, but did not affect race day. This was the most recent Indy 500 scheduled for Thursday; the Uniform Monday Holiday Act was implemented in 1971 and Memorial Day became a three-day weekend (Saturday–Monday) every year. A day previously avoided, Sunday became the scheduled race day beginning in 1974. Race schedule Time trials was scheduled for four days, but for the first time under the current schedule format, qualifying was carried over into a fifth day. Most of Bump Day (May 26) was rained out, and the track closed due to darkness with the field not yet filled to 33 cars. A special session was held Monday in order to complete the field. The 500 Festival Parade was held Tuesday night, May 28. Practice and time trials The 1968 Indianapolis 500 was the second and ultimately the final year of participation by the controversial STP Granatelli Turbine machines. For 1968, the Pratt & Whitney turbine engine was installed in the Lotus 56 chassis, often known colloquially as the "Wedge Turbine," and sometimes