1991 Michigan 500

The 1991 Marlboro 500, the eleventh running of the event, was held at the Michigan International Speedway in Brooklyn, Michigan, on Sunday, August 4, 1991. Branded as the 1991 Marlboro 500 for sponsorship reasons, the race was won by Rick Mears, his final Indy Car victory. It was also Mears' only win in the Michigan 500. The event was race number 11 of 17 in the 1991 CART PPG Indy Car World Series. 42°03′58.68″N 84°14′29.18″W / 42.0663000°N 84.2414389°W / 42.0663000; -84.2414389

In May, Rick Mears won the Indianapolis 500 for a record-tying fourth time.

By 1991, the Chevy Indy V-8 engine had won every Indy car race since September 1989. The dominant engine was necessary for teams to compete for wins. Entering the Michigan 500, Ilmor announced they had approved engine leases for 1992 for the Dick Simon-owned car of Hiro Matsushita and deny leases to Patrick Racing and Truesports. Some believed the denials for the teams were political. In 1989, Patrick Racing left Chevrolet for Alfa Romeo and sent a Chevrolet engine to Alfa Romeo to copy for development. Truesports had led the development of the Judd engine. The controversy over who was allowed to lease engines was called "an embarrassment to CART" by journalist Robin Miller.

Practice began on Thursday, August 1. Emerson Fittipaldi set the fastest speed at 224.134 mph. Rick Mears was second fastest at 223.678 mph. Mario Andretti was third at 223.653 mph.

Arie Luyendyk was sidelined from practice after Total Petroleum obtained a restraining order to prevent his Vince Granatelli team from racing. Granatelli had partnered to co-own the team with Bob Tezak, a partnership that was dissolved in June. Granatelli pulled Total logos from the car, claiming their deal was with Tezak and not a part of the team going forward. Total demanded the logos remain on the car and went to court over it. Until the dispute was dissolved, Luyendyk and the team were forbidden from competing in IndyCar. Luyendyk was also suing Tezak for missed salary payments.

On Friday afternoon, Rick Mears won the pole at a speed of 225.169 mph, breaking the track record he set in the 1986 Michigan 500. The slowest qualifier was John Jones with a speed of 200.198 mph. Emerson Fittipaldi joined Mears on the front row.

A. J. Foyt suffered a blown engine in practice on Friday morning. His crew rushed to change the engine and was told he would be able to qualify at his drawn position. When the car was presented at the qualifying line, the crew was told they were too late and would have to go to the rear of the qualifying line, plus be penalized one of their two qualifying laps. Foyt called the penalty a "cheap shot" by CART. Foyt withdrew from the race and loaded his equipment back onto the hauler. After meetings with MIS track president Walt Czarnecki and CART President Johnny Capels, Foyt announced he would reconsider his participation in the event. On Saturday morning, Foyt announced he would compete.

A court hearing in a Detroit dissolved the restraining order and denied an injunction against the Granatelli team and allowed Luyendyk to begin activities on Saturday.