Fuelling up with cheaper petrol has left a Wellington couple out of pocket by more than $7000.
And, despite taking a claim to the Motor Vehicle Disputes Tribunal, they won't be getting their money back.
Aron and Adelle Bailey complained they were never told by the car yard that sold them their Volkswagen Sharan that the European car must be fuelled with 95 octane petrol, rather than the cheaper 91 octane.
There was also no sticker on the fuel filling area to indicate which should be used.
In July last year, 23 months and 13,000km after they bought the car, the couple's mechanic told them damage to a piston was likely caused by their use of 91 octane petrol, according to the tribunal findings.
The engine cost $7576 to repair and the couple wanted Gazley Motors to pay. They also claimed Gazley Motors failed to service the direct-shift gearbox transmission before selling them the vehicle.
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Gazley Motors agreed to pay for the transmission service, but said - although there was no evidence fuel type advice was given - it was normal practice to advise customers which fuel they should use.
They said they would only make a $1000 "goodwill" payment to the couple, an offer later retracted.
The couple argued Gazley Motors should have told them the car was designed to use 95 octane petrol, adjudicator Jason McHerron wrote in his decision.
"I agree this would have been preferable. However, whether or not Gazley Motors advised Mrs and Mrs Bailey what octane fuel to use, I do not consider it was Gazley Motors' fault the wrong fuel was used ... it is not the responsibility of a motor vehicle trader to positively disclose such information.
"Rather it's the consumer's responsibility to make the necessary inquiries to determine what sort of fuel should be used in a vehicle."