Fair Go goes in to bat for woman blamed for putting dirty fuel into her brand new Mazda CX-8

Have you ever been sure of something? So sure that you couldn't be convinced otherwise, until suddenly you realised you were wrong all along?

Psychologists call this confirmation bias. If you answered yes, congratulations - it means you're only human.

You're no different from the people who sold Prashila Edwards a brand-new car fuelled by tankfuls of diesel to get her and her family where she was going.

We say tankfuls – we mean five – because Prashila had only filled up that many times in seven months before the car conked out.

That is not what anyone expects from a top of the line Mazda CX-8 LTD priced at $62,000.

It was a bit of a mystery and everyone involved seemed to be convinced it wasn't their problem.

"Apparently it broke down due to fuel contamination and because it was a contaminant we put into the car, the mechanical warranty didn't cover it," Prashila tells Fair Go.

"What, am I meant to test my fuel every time I go to the petrol station?", she wonders.

The car also has cover under a comprehensive policy with AA Insurance, but it specifically excludes losses caused by contamination.

"These losses aren't sudden and accidental in nature - they can be prevented," AA Insurance Head of Product Aaron Dickinson told Fair Go.

"The party responsible for the original problem should provide a resolution."

Mazda blames dirty diesel but fuel companies say their fuel is clean.

Z Energy has given Prashila heaps of data following her one fill with them but BP didn't say as much about its four fills - until Fair Go asked to see the homework.

BP's homework holds up to scrutiny and AA can show it has offered some assistance but crossed wires mean it wasn't called on.

Mazda, on the other hand, agrees to foot the bill and cover the cost of repair work, which revealed the problem all along has been an injector fault in the vehicle, which should have been picked up straight away – and fixed at Mazda's cost.

For eight weeks Prashila had been using a loan car which was also the amount of time the dealer spent testing and retesting the fuel which put Prashila on the hook for a big repair bill.

"Because contaminated fuel was the focus, there was considerable time spent going back and forward to a fuel test company, arranging for fuel to be tested, and parts replaced," says Mazda NZ national service manager John Van Der Velden.

What he describes happening at the dealership is a classic case of confirmation bias. Seeing what you want to see. Looking only for what you hope to find. Forgetting about what doesn’t fit. Simple human frailty. It takes an effort to keep an open mind. Or, a bit of a jolt from the outside.

It pays to learn your lesson and John Andrew Mazda wants to show they've learnt theirs. Prashila is back behind the wheel and with a bit of a sweetener - a family weekend away in Rotorua or Taupo, and two months' free diesel, to say sorry for causing unnecessary stress.

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There were many issues to sort as we try and get a resolution for Prashila. Source: Fair Go