The Ministry of Consumer Affairs is keen to investigate reports of modern diesel vehicles whose engines have been damaged or destroyed by fuel contamination.
Some owners are complaining about having to pay several thousand dollars for repairs on vehicles, some of which are only just out of warranty.
The car buyers' publication Dog and Lemon Guide says there's a growing but unacknowledged problem with modern diesel engines, which are susceptible to fuel contamination - and it's urgent the Government investigates.
It says, in some cases, filters are not up to the task of blocking water, dirt and other contaminants.
However, car manufacturers say their filters are fine and the problem is in the way fuel is stored and handled.
The Ministry of Consumer Affairs has received only two complaints about the issue in the past year, and is keen to hear from owners so it can investigate.
Stephen O'Brien from the ministry says evidence so far has been anecdotal, and is asking aggrieved car owners to email or phone the ministry's fuel monitoring unit.