The 1991 CART PPG Indy Car World Series season was the 13th national championship season of American open wheel racing sanctioned by CART. The season consisted of 17 races, and one non-points exhibition event. Michael Andretti was the national champion, and the rookie of the year was his younger brother Jeff Andretti.
The 1991 Indianapolis 500 was sanctioned by USAC, but counted towards the CART points championship. Rick Mears won the Indy 500, his record-tying fourth victory in the event.
Michael Andretti won a total of eight races, eight pole positions, and led more than half of the laps during the season, but the championship battle still went down to the final race of the season. Bobby Rahal won only one race, but had 11 podium finishes and 13 top tens. Rahal's consistent season put him in position to challenge Andretti for the title in the season finale at Laguna Seca. Andretti got off to a slow start to the season, dropping out of the first two races, and finished a heartbreaking second at Indianapolis. But after Indy, he shot to the top of the standings. He won four of the last five races of the season, and needed to finish 6th or better at Laguna Seca to clinch the title. When Bobby Rahal dropped out at Laguna Seca with overheating problems, Andretti cruised to the title. Taken from http://en.wikipedia.org/wiki/1991_CART_PPG_Indy_Car_World_Series.

Race Results:

	Date	Site	Cars	Winner(s)	St	Chassis / Engine	Miles	Pole	Cau	Laps	Speed	LC	Time of Race
CART	3/17/1991	Queensland	25	John Andretti	9	Lola / Chevrolet	182	100.501	3	15	81.953	4	2:12
CART	4/14/1991	Long Beach	26	Al Unser, Jr.	2	Lola / Chevrolet	159	90.671	1	9	81.195	3	1:57
CART	4/21/1991	Phoenix	22	Arie Luyendyk	9	Lola / Chevrolet	200	168.334	3	23	129.988	6	1:32
USAC	5/26/1991	Indianapolis	33	Rick Mears	1	Penske / Chevrolet	500	224.113	7	35	176.457	18	2:50
CART	6/2/1991	Milwaukee	21	Michael Andretti	3	Lola / Chevrolet	200	162.264	2	12	134.577	7	1:29
CART	6/16/1991	Detroit	25	Emerson Fittipaldi	2	Penske / Chevrolet	156	88.721	2	6	79.455	6	1:57
CART	6/23/1991	Portland	23	Michael Andretti	4	Lola / Chevrolet	200	122.47	0	0	115.208	5	1:44
CART	7/7/1991	Cleveland	23	Michael Andretti	2	Lola / Chevrolet	201	140.842	2	10	117.763	6	1:42
CART	7/14/1991	Meadowlands	23	Bobby Rahal	4	Lola / Chevrolet	183	115.991	4	19	95.551	1	1:54
CART	7/21/1991	Toronto	23	Michael Andretti	1	Lola / Chevrolet	183	108.469	1	4	99.143	0	1:50
CART	8/4/1991	Michigan	21	Rick Mears	1	Penske / Chevrolet	500	225.169	9	52	167.23	18	2:59
CART	8/25/1991	Denver	24	Al Unser, Jr.	3	Lola / Chevrolet	133	79.631	3	11	69.576	1	1:57
CART	9/1/1991	Vancouver	22	Michael Andretti	1	Lola / Chevrolet	168	105.205	1	7	93.888	5	1:47
CART	9/15/1991	Mid-Ohio	24	Michael Andretti	1	Lola / Chevrolet	200	116.589	3	14	99.789	2	1:59
CART	9/22/1991	Elkhart Lake	25	Michael Andretti	3	Lola / Chevrolet	200	134.466	0	0	126.205	6	1:35
CART	10/6/1991	Nazareth	21	Arie Luyendyk	11	Lola / Chevrolet	200	178.74	2	30	131.31	7	1:31
CART	10/20/1991	Laguna Seca	27	Michael Andretti	1	Lola / Chevrolet	186	110.555	0	0	103.604	0	1:47