Mr Mullan founded one of Northern Ireland’s largest and first large-scale car supermarkets, Bob Mullan Motors, in Ballykelly in 1980.
One of NI's most successful car businesses, it later moved to a new site at Campsie in Eglinton.
He was best-known in Irish motorcycling circles as the sponsor of top Coleraine rider Owen McNally, who died following a crash at the Ulster Grand Prix in 1999.
A father of seven, Mr Mullan – who died at Altnagelvin Hospital – was also a valued sponsor of the North West 200 for many years.
Billy Nutt, Clerk of the Course at the North West 200 from 1973 to 2000, told the News Letter: “Bobby was some character as far as motorbikes was concerned. He was very good to us both in terms of the North West 200 and also with my son Marty when he was racing.
“He supplied us with cars and vans and was a great help. With the North West, Bobby did so many things that probably a lot of people didn’t know about – he was a great supporter of the event. He lent a lot of cars to various people and gave us a lot of support.
“Bobby was a great supporter of Owen McNally and it was one of the highlights of my involvement with the North West 200 when Owen won the 250cc race on Bobby’s Aprilia in 1997,” added Nutt.
“Owen lived on the course, Bobby was a local man and Owen was very good to Marty when he first started out racing, so it was a fantastic day when he won.
“Bobby was just a civil being and he was a good guy. When I heard the news on Monday I just thought, ‘ah no’. It’s sad.”
Mervyn Whyte, who took over the reins at the North West 200 following Nutt’s retirement before standing down as Event Director last October, said Mr Mullan’s death was ‘the end of an era’.
“Bobby had been in hospital for a couple of weeks in intensive care and sadly he passed away on Monday morning,” said Whyte.
“I couldn’t believe it because I didn’t think it was as serious as it was. He wasn’t terribly old and I believe he was around 68 or 69. It’s a sad loss and Bobby was involved in sponsorship of the North West from away back.
“He was always very supportive of the event itself and for a number of years he provided us with course vehicles, and he also gave a lot of vehicles to the competitors themselves.
“Bobby was always there to provide any help that you needed and he was a great financial help to us at the end of the day. In 2009/2010 he sponsored the new lighting system that we introduced for the first time. He paid for the whole thing and that was a great help at the time,” added Whyte.
“He was an absolute gentleman and was always on hand to help when he could.
“As everyone knows he sponsored Owen McNally back in the day and they had plenty of success together, but unfortunately Owen was killed at the Ulster Grand Prix.
“It’s the end of an era now that Bobby’s gone, there’s no doubt about it; it’s a sad loss, especially for his family.”
Requiem Mass will take place on Wednesday at Star of the Sea church, Faughanvale at 3pm, with interment afterwards at St Finlough’s cemetery in Ballykelly.