The Mercedes Benz G-Class SUV afforded him the kind of direct contact with people he has embraced since becoming pope.
Had he been in the Popemobile, he would have been behind bulletproof glass, which was installed in 1981 after an assassination attempt on John Paul II.
Filipino priest and CNN iReporter Joel Camaya, who was among those in St. Peter's Square, was enthralled by the spectacle, and the contrasting humility, of the newly elected pontiff.
"The Pope spoke with such passion and force that the words exuded life and thus, as he spoke, there were instances of spontaneous applause," he said. "In the piazza, people who haven't even known each other exchanged smiles, happy that they belonged to one big family."
Francis called his predecessor, Pope Emeritus Benedict XVI, Monday afternoon to wish him well on the day of the Feast of St. Joseph and to thank him again for his service. Benedict, in turn, said he had been following the events since Francis' selection closely and assured his closeness in prayer.
Style or substance?
The Mass which inaugurated Francis as bishop of Rome and marked the official start of his papacy was short, lasting about two hours. This was in keeping with the spirit of simplicity embraced by the new pontiff, the Vatican said before the occasion.
Francis has already made an impression as a pope of the people who is concerned about the welfare of the poor. But he inherits a church wracked by a decades-old sexual abuse scandal and claims of corruption in the clergy.
Monsignor Kevin Irwin told CNN the Catholic Church probably would not have to wait long before the changes in style already seen under Francis become changes in substance.
"It comes down to personnel," he said. "The personnel changes you make in any corporation make all the difference. Leadership matters -- but then who are the other people who help implement his program?"
The Vatican said Saturday that Francis had provisionally confirmed members of the Vatican hierarchy in their positions, but would take time to reflect before any final appointments are confirmed.
Irwin said he believes the key changes are likely to come in the late spring or early summer.
Francis, as a member of the Jesuit order, "gets into things" and is tenacious, he said. "This is a 'take-charge' pope, I would say."
Back in St. Peter's Basilica, the newly installed bishop of Rome greeted the dignitaries who had flocked from around the world to attend the inauguration Mass.
President Cristina Fernandez de Kirchner, from Francis' native Argentina, was the first head of state to step up.
Vice President Joe Biden, leading the U.S. presidential delegation, was also among those to meet the 76-year-old pope, as was Zimbabwe's controversial President Robert Mugabe.
Mugabe is subject to a European Union travel ban but allowed to visit the continent for religious events and international conferences.
Vatican Secretary of State Cardinal Tarcisio Bertone -- effectively the Vatican's prime minister -- was at the pope's side as, standing, he gave his greetings for close to an hour and a half.
The formal encounters over, Francis then went to the barriers around the sides of the basilica to greet priests, nuns and other well-wishers.