No. Today, all teams do use the same car in the series, but back in the day a few different manufactures built the machines.
In order: Mario Andretti's Ford powered Lola from 1993
Al Unser Jr.s Indy 500 winning Mercedes powered Penske from 1994
Emerson Fittipaldi's Mercedes powered Penske from 1996
Bobby Rahal's championship winning Chevrolet powered Lola from 1992
Michael Andretti's Lola-Ford from 1996
Alex Zanardi's championship winning Reynard-Honda from 1997
and Dario Franchitti's Lola-Honda from 2003