In 1987, Penske's slate of drivers included Rick Mears, Danny Sullivan, and Danny Ongais.
Al Unser Sr.
was dropped from the team, and entered the month of May without a ride.
During the first week of practice, Al Sr.
spent much of the week shopping for a ride, and a few offers were made by owners.
Al Sr.,
however, refused the offers, as he insisted on landing a ride in a competitive, well-funded car only.
Unser planned on staying through the week, and if he did not have a ride by the end of the first week of time trials, he was planning to return home.
Coincidentally, his son Al Unser Jr. (driving for Shierson Racing) was having difficulty with his car's handling.
At the end of the first weekend of time trials, Al Jr. surprisingly had not yet qualified.
Al Sr.
agreed to stay through the week in order to help his son get his car up to speed.

Danny Ongais crashed into the wall during the first week of practice, suffering a serious concussion, and was declared unfit to drive.
Meanwhile, the Penske team's new Penske PC-16 chassis had been uncompetitive during practice.
By the end of the first week of practice, Penske parked the PC-16s and elected to qualify back-up cars for the race.
Mears and Sullivan were provided 1986 March-Ilmor Chevrolet machines, while a third car, a 1986 March-Cosworth, was planned for third driver.

Midway through the second week of practice, Roger Penske consummated a deal with Al Sr.
to drive the third car.
Penske promised Unser a well-funded effort, and a brand new Cosworth engine, the same chassis/engine combination that had won the previous four Indy 500s.
The year-old March was removed from a Penske Racing display at a Sheraton hotel in the team's hometown of Reading, Pennsylvania, and hurriedly prepared for a return to active competition.
Unser easily put the car in the field on the third day of time trials.

At the start Unser was in the 20th position.
On a day when heavy attrition felled most of the field's front-runners, including the overwhelmingly dominant Newman-Haas entry of Mario Andretti, Unser worked his way steadily forward and took the lead on the 183rd lap, after Roberto Guerrero's car stalled on his final pit stop.
Averaging 162.175 mph (260.995 km/h), Unser bested a charging Guerrero by 4.5 seconds to win his fourth Indy 500, only five days before his 48th birthday.
In doing so he tied Foyt as the winningest Indy 500 driver and broke brother Bobby's record as the oldest Indy winner.

Unser rode the wave of his fourth Indy victory to secure a ride at Penske for the Michigan 500, Pocono 500, and Marlboro Challenge for 1987.
Near the end of the year, Unser had two other starts.
He drove as a substitute for Roberto Guerrero at Nazareth, and had a competitive run until crashing a few laps short of the finish.
He was then hired to drive the brand new Porsche Indy car at Laguna Seca.
The team was still in its infancy, and the car dropped out.
Unser left the team after only one race.

In 1988 and 1989, Unser returned to Penske to secure a ride at the three 500-miles races (Indianapolis, Michigan, Pocono).
In 1987, Penske's slate of drivers included Rick Mears, Danny Sullivan, and Danny Ongais. Al Unser Sr. was dropped from the team, and entered the month of May without a ride. During the first week of practice, Al Sr. spent much of the week shopping for a ride, and a few offers were made by owners. Al Sr., however, refused the offers, as he insisted on landing a ride in a competitive, well-funded car only. Unser planned on staying through the week, and if he did not have a ride by the end of the first week of time trials, he was planning to return home. Coincidentally, his son Al Unser Jr. (driving for Shierson Racing) was having difficulty with his car's handling. At the end of the first weekend of time trials, Al Jr. surprisingly had not yet qualified. Al Sr. agreed to stay through the week in order to help his son get his car up to speed. 
Danny Ongais crashed into the wall during the first week of practice, suffering a serious concussion, and was declared unfit to drive. Meanwhile, the Penske team's new Penske PC-16 chassis had been uncompetitive during practice. By the end of the first week of practice, Penske parked the PC-16s and elected to qualify back-up cars for the race. Mears and Sullivan were provided 1986 March-Ilmor Chevrolet machines, while a third car, a 1986 March-Cosworth, was planned for third driver.
Midway through the second week of practice, Roger Penske consummated a deal with Al Sr. to drive the third car. Penske promised Unser a well-funded effort, and a brand new Cosworth engine, the same chassis/engine combination that had won the previous four Indy 500s. The year-old March was removed from a Penske Racing display at a Sheraton hotel in the team's hometown of Reading, Pennsylvania, and hurriedly prepared for a return to active competition. Unser easily put the car in the field on the third day of time trials.
At the start Unser was in the 20th position. On a day when heavy attrition felled most of the field's front-runners, including the overwhelmingly dominant Newman-Haas entry of Mario Andretti, Unser worked his way steadily forward and took the lead on the 183rd lap, after Roberto Guerrero's car stalled on his final pit stop. Averaging 162.175 mph (260.995 km/h), Unser bested a charging Guerrero by 4.5 seconds to win his fourth Indy 500, only five days before his 48th birthday. In doing so he tied Foyt as the winningest Indy 500 driver and broke brother Bobby's record as the oldest Indy winner.
Unser rode the wave of his fourth Indy victory to secure a ride at Penske for the Michigan 500, Pocono 500, and Marlboro Challenge for 1987. Near the end of the year, Unser had two other starts. He drove as a substitute for Roberto Guerrero at Nazareth, and had a competitive run until crashing a few laps short of the finish. He was then hired to drive the brand new Porsche Indy car at Laguna Seca. The team was still in its infancy, and the car dropped out. Unser left the team after only one race.
In 1988 and 1989, Unser returned to Penske to secure a ride at the three 500-miles races (Indianapolis, Michigan, Pocono).
Al Unser