Granado, an Argentine biochemist who had lived in Cuba since 1961, died Saturday of natural causes, according to Cuban state-run television, which gave no other details.
Granado and Guevara's road trip, begun on a broken-down British Norton motorcycle they dubbed La Poderosa, or "The Powerful," awoke in Guevara the social consciousness and political convictions that helped turn him into one of the most iconic revolutionaries of the 20th century.
The travelers each kept diaries that were eventually published, Guevara's as "The Motorcycle Diaries: Notes on a Latin American Journey" and Granado's as "Traveling With Che Guevara: The Making of a Revolutionary." Their accounts were used as background for the 2004 movie directed by Brazilian Walter Salles and starring Argentine actor Rodrigo De la Serna as Granado and Mexico's Gael García Bernal as Guevara.
"The diaries were written for ourselves," Granado told London's Independent newspaper in 2004. "Neither of us ever thought for a moment they would be published. The film shows what we were, which was two young men — boys, really — who went looking for adventure and found the truth and the tragedy of our homeland."
Granado was born Aug. 8, 1922, in Hernando in the Cordoba province of central Argentina, where his father worked for the railroad. He studied at the University of Cordoba.
In his 1997 biography of Guevara, Jon Lee Anderson wrote that Granado was "barely five feet tall and had a huge beaked nose, but he sported a barrel chest and a footballer's sturdy bowed legs; he also possessed a good sense of humor and a taste for wine, girls, literature and rugby."
As young medical students, Granado and Guevara witnessed deep poverty across the continent — principally in Chile, Colombia, Peru and Venezuela — during their eight-month, 8,000-mile odyssey, and their stay at a Peruvian leper colony left a particularly deep impression.
They parted ways in Venezuela, where Granado stayed on to work at a clinic treating leprosy patients. Guevara went to Miami, then returned to Buenos Aires to finish his studies.
Guevara later joined Fidel and Raul Castro as they sailed from exile in Mexico to Cuba in 1956. Their small band of rebels ultimately toppled dictator Fulgencio Batista on New Year's Day 1959.
Guevara was captured and killed by soldiers in Bolivia in 1967 as he tried to foment revolution in the Andean nation.
Granado visited Cuba at Guevara's invitation in 1960 and moved to Havana the next year with his family. He had lived in Cuba ever since, founding the Santiago School of Medicine and teaching at various Cuban universities.
"There are three things that have affected my life," Granado told the South Florida Sun-Sentinel in 2004. "The first was meeting Ernesto. The second was the [motorcycle] trip. The third was to join the Cuban revolution."