Barry Dell Plumbing owner Barry Carmichael said the ''very strange criminal'' responsible for the theft had taken the least useful vehicle in the company's yard.''
Of all the vehicles in the yard, it's the oldest,'' he said.
''It's got one specific use. It's quite weird. It's like they stole it to order. I just don't know. I've got no idea what he's going to use it for.''
The vehicle was bright blue and yellow and heavily sign-written with ''Barry Dell Plumbing'' on its side and is used for emptying sumps and mud traps.
''It's not as if it's hard to spot,'' Mr Dell said.
Adding to the intrigue was how slow the truck was to drive.
''It probably only goes 80kmh - flat out, down a hill, with a wind behind it,'' he said.
''I don't think he's [the thief] the brightest cookie in the jar.''
He called on the man to return the vehicle and for members of the public to report sightings of it to police or the company.
A Barry Dell Plumbing spokesman who has been tracing the journey of the truck said the vehicle had been used in several petrol thefts before leaving Dunedin on Tuesday morning.
The thief had convinced petrol station attendants he had lost the truck's fuel card and would return later to pay for petrol and, in one instance, he mistakenly filled the petrol-powered truck with diesel.
''He thought this thing's running like a bag of s... and that's because the thing runs on petrol,'' the spokesman said.
The thief emptied the $58 of diesel in its tank into the street in Dolphin St, in Northeast Valley. He then used his own eftpos card to buy small quantities of petrol in a petrol can that he borrowed using his own passport as collateral, the spokesman said.
The truck was then used to steal petrol from a North Dunedin petrol station and was driven out of Dunedin.
Sightings from Oamaru, Timaru, Winchester and Ashburton had been reported.
The spokesman said he was surprised the vehicle had lasted the ''tiki tour''.
''We would never run it that far. The poor old girl couldn't take it. We would have staff leave if we asked them to drive it to Christchurch.''
Southern police spokesman Nic Barkley said officers were also puzzled by the motivation behind the theft.
''Police are still not sure of why the truck was stolen or where it is headed, but are asking members of the public to keep an eye out and report any sightings directly to police,'' he said.
Two men were spotted getting into the vehicle in central Dunedin shortly after it was stolen on Tuesday morning.
The pair were seen in the Octagon Night 'n Day about 5.25am. They entered the store and left separately before getting back into the truck and heading north.
Police were unsure whether both men remained with the truck, but officers throughout the South Island had been alerted to the theft, he said.
Police want to hear from anyone who knows the two men and ask them to contact their local police station.
Alternatively, information can be provided anonymously via the organisation Crimestoppers on 0800 555-111.
