The day of the episcopal ordination saw the participation of numerous members of the Salesian Family, first of all, the new Rector Major Fr Renato Ziggiotti, of the diocesan clergy, of many acquaintances and friends of Diano d'Alba, his town of origin, of family members, including his mother Agostina, his brother Fr Giuseppe, a diocesan priest, and his sister Sister Agnese, as well as the elderly teacher Caterina Zannone. The consecrating was by cardinal Maurilio Fossati, archbishop of Turin, and co-consecrating was the bishop of Alba, Msgr. Carlo Stoppa, and the auxiliary of the bishop of Tortona, Msgr. Carlo Angeleri. At the end of the meal, at the moment of thanksgiving, the new bishop declared: "Feeling so much pressure to become a bishop, I finally convinced myself that in the end, I too had to have some dowry to become a bishop. And by dint of thinking about it, I found it in Saint Paul: Infirma et stulta elegit Deus ut confundat fortia [1 Cor 1:27]. May the superiors continue to help me.”
The Eucharist was presided over by Monsignor Marco Brunetti, Bishop of Alba, who in his homily, referring to the liturgical feast of St. John the Apostle and Evangelist, spoke of Monsignor Marengo: “No one can fail to notice John's reference to the senses that every man has for knowing and perceiving reality: in particular, John speaks of hearing, seeing and touching. The Beloved Disciple thus speaks of a verifiable experience: if the Word of God became flesh, it means that there is no relationship with God that does not pass through the "flesh", that is, the concrete experience of every day. This reminds us of Msgr. Marengo's testimony that we do not encounter God in our ascetical journeys but in our daily lives and in particular when, for the people and for India, whom he loved, he had learned the many languages, the dialects that he spoke correctly, as well as the universal language of love that had guided him throughout his life. Founding father of three dioceses; the bishop who had never retired. In a few words, Don Bosco's philosophy and example had taken shape in his person.”
Fr Pierluigi Cameroni, Postulator General, after having presented the chronicle of the appointment and episcopal consecration of Mons. Marengo, spoke of him as the bearer of hope. Mons. Oreste Marengo was the first bishop of the Diocese of Dibrugarh from 1951 until 1964, the year in which he was appointed bishop of the nascent Diocese of Tezpur. He remained bishop in Tezpur until 1969, facing hostilities from the Indian government which opposed foreign missionaries and thus giving way to an Indian successor. Appointed apostolic administrator of the new Diocese of Tura in 1972, he held it until 1978, when his successor, a local Indian, Msgr. Mamalassery, was appointed.
He continued for many years to serve in the missions and to collect funds for the Diocese of Tura, maintaining a close correspondence with benefactors and friends from various countries around the world who supported him throughout his missionary and episcopal activities. His entire ministry - carried out more on the road, at the various tribes entrusted to him, than at the bishop's seat - was a continuous effort to bring and build conditions of hope among very poor people, affected by hunger, earthquakes and floods, numerous diseases, armed conflicts with neighboring China, the tragedy of being forcibly expatriated from their homelands. Above all, he incarnated the newness of the Gospel by meeting the little ones and the poor, recognizing in them the signs of grace and announcing with kindness the joy of the Gospel.
