The couple spent more than $140,000 on a new Volkswagen Touran TDI 1.6, which they collected on Sept 21.
Three months on, Cheah Khuan Yew, 37, and his wife Jessica, 41, have found themselves saddled with a $28,000 bill.
The engine and fuel system of their car have been ruined as a result of water tainting the diesel in the fuel tank, and have to be replaced.
The couple, who are in the banking industry, are baffled over how the water got into the diesel.
"We were told it's premature ageing. Basically, it's like a three-year-old car with a 10-year-old engine," said Mr Cheah, drawing his own analogy to show the extent of damage.
"It's been almost three months. As a consumer, I buy a car to drive. I'm not buying a risky puzzle."
They told The New Paper last Friday that they first noticed the problem just days after they bought the diesel-powered car.
It was meant to replace their seven-year-old second-hand Honda Civic, which they used mostly on weekends or to take their three children to school.
But after Mr Cheah pumped diesel into the four-day-old car at an Esso service station, things started going awry.
When Mrs Cheah drove the car the next day, she noticed that it "felt funny".
The engine was stuttering, the tachometer fluctuating even when the engine was idling.
"I thought it was just a one-off thing. A woman is not so sensitive to car-related things," she said.
But when her husband also noticed the problem, they realised that something was not right.
On Oct 3, the couple took their seven-seater to the Volkswagen Centre in MacPherson Road, as advised by the staff member manning the Volkswagen Roadside Assistance hotline.
They were told that the car had been damaged, probably due to tainted diesel.
"They said it was not covered (under the warranty). I couldn't believe it. It's a brand new car," Mrs Cheah said, recalling her exchange with the Volkswagen staff member.
An analysis of a sample of the diesel as part of a preliminary test found the water content to be higher than what is allowed in the Euro V standard for diesel.
The car was then sent to the Volkswagen Centre in Alexandra Road for further inspection.
In the interim, Volkswagen loaned the Cheahs a courtesy car.
On four occasions in October and last month, Volkswagen hired LKK Auto Consultants to assess the damage to the car.
A Volkswagen Group Singapore spokesman confirmed this. "We have since carried out an investigation on this case and a third-party surveyor discovered there was water content in the fuel tank," he said.
In its report, LKK Auto Consultants found that the engine stuttering was due to low compression of air. When that happens in a diesel engine, the fuel cannot be ignited and the car stalls.
According to the report, the low compression was a result of damaged parts in the car's engine, likely due to the presence of excess water in the diesel.
"The water content that was contained in the diesel of the motor car was likely due to external factor(s) and unlikely to be a result of manufacturer defect(s)," the report said.
The recommendation was to replace the entire engine and fuel system of the car.
But the couple continue to be baffled with the report's conclusion, especially after meeting ExxonMobil representatives last Thursday.
During the meeting, the couple were presented with reports analysing the fuel quality and how equipment monitoring the fuel is set up.
"ExxonMobil showed us various reports. They presented a very clear, watertight case that it's not a fuel problem," said Mrs Cheah.
In addition, 261 other customers had gone to the same Esso station that day, but none reported a problem similar to the Cheahs'.
Said Mr Cheah: "We're satisfied that there's no problem on ExxonMobil's side. We've checked the only external factor - pumping tainted diesel into the car - and there's proof that it is not contaminated. So then the question is: Where is it coming from?"
The couple also considered the possibility of someone pouring water into the fuel tank out of mischief.
"But the fuel tank cover can only be opened by a button inside the car, and we found no signs of tampering or scratches on the fuel cover," Mr Cheah said.
The couple feel helpless as consumers. There is the lemon law, but it is only enforceable if the retailer obliges, Mr Cheah said.
"We're both working professionals who are conversant enough to write letters. What if it's someone who's not so well-educated, can you imagine the struggle he has to go through?" he said.
"At the end of the day, as a consumer, I just expect a car that works."
Agreeing, Mrs Cheah said: "We shouldn't be burdened with this, right?"
But time is not on their side, as the couple have been notified by Volkswagen to decide whether to go ahead with the repairs by Friday.
It will cost about $19,000 to replace the engine and another $9,000 to replace the fuel system, including labour costs.
This amount is not covered by the car's five-year warranty or the annually-renewed insurance, as the former does not cover anything due to external factors and the latter only covers accidents.
The couple are undecided on what to do next.
This article by The New Paper was published in MyPaper, a free, bilingual newspaper published by Singapore Press Holdings.