The vehicle is a high-performance variant of the Ford F-150, modified by Shelby American and commonly referred to as the “Shelby F-150”, and has a supercharged 5.0L V8 engine with a 700-horsepower rating.
After two-and-a-half years of use, the engine catastrophically failed after doing just 45,000km.
Harrison told NZME they purchased the truck with money she inherited when her father passed away, thinking it was going to be the car they had for the rest of their lives.
“I thought it would be our last vehicle,” she said.
“It was the dream car … now it’s turned into a nightmare.”
They were advised by the dealer, 4 Guys Autobarn in Hamilton, that the vehicle could use 95-octane petrol when 98-octane wasn’t available.
The requirement for using 95-octane is listed in brochures for the vehicle, user manuals, as well as specifications for tuning the vehicle. However, those same documents also recommend using 98-octane if possible.
Despite the couple driving the vehicle conservatively, servicing it regularly, and using 98-octane when it was available, according to the tribunal, they began noticing a rattling sound underfoot on the front passenger side of the car.
The car was serviced, but the sound remained, and it was recommended that the catalytic converters be replaced.
Despite Shelby New Zealand noting that it was unusual for low-mileage vehicles to need their catalytic converters replaced, it carried out the repairs anyway.
However, after being returned to the couple, the car began misfiring above 4000rpm, and it was taken back to Shelby NZ, which had it for several weeks in March before the couple were asked to collect it.
As they drove away, the couple said the car began billowing smoke so badly they thought there was a car fire behind them.
A mechanic who assessed the vehicle found that the engine had failed entirely.
Harrison said the couple has since spent close to $40,000 repairing the truck, most of that on a new engine.
“We’re not sure if we even want to keep it any more. This whole thing has put a bit of a taint on things,” Harrison said.
Dealer recommended wrong fuel
Harrison and Neil filed a claim with the tribunal for both 4 Guys and Shelby NZ to be liable for the engine failure.
Their argument was that 4 Guys told them 95-octane would suffice, and that Shelby did more damage to the vehicle when they took it in for repairs.
4 Guys maintained that 95-octane was the right fuel to use, and, if anyone was at fault, it was Shelby because the vehicle was running fine before its mechanics worked on the catalytic converters.
Shelby NZ says that 95-octane should never have been used in the vehicle and that the couple should have used 98-octane exclusively.
Tribunal adjudicator Crystal Euden found that while the engine did fail because a lower octane fuel was used, it was neither the dealers’ nor Shelby NZ’s fault.
“It is likely that the engine would have failed sooner had the purchasers not used 98-octane fuel when it was available and not driven the vehicle as conservatively as they did,” Euden found.
Euden said that by the time the vehicle went into Shelby NZ for repairs, it was already too late and that “Shelby NZ’s involvement and the vehicle’s retuning simply accelerated a failure that was already inevitable due to the pre-existing engine damage”.
As for 4 Guys, Euden said that while the Consumer Guarantees Act protected buyers, it had a limit, and, at some point, the risk of a vehicle developing significant defects became the purchaser’s problem.
“Here, the purchasers bought a six‑year‑old, second‑hand vehicle. Although its mileage was low and it cost a significant sum, they drove it for two-and-a-half years and over 50,000 km before any faults became apparent,” Euden said.
While 4 Guys recommended the wrong fuel, Euden said that it was the dealer’s opinion that it was the right fuel and would not cause harm to the vehicle.
“All the documentation regarding the vehicle at the time, and still today, is that 91 AKI or 95-octane fuel, at a minimum, is fine for the vehicle,” Euden said.
“While it is apparent from the evidence that 98-octane fuel was the preferred and more appropriate fuel for the purchasers’ vehicle, 4 Guys’ opinion that 95-octane fuel should be used was both honestly held and reasonable at the time the vehicle was sold.”
‘To be safe, you need to be using 98 in these vehicles’
The operations manager for Shelby NZ, Ross Prevette, told NZME that if the couple had purchased their car directly from him, he would have told them to use 98-octane or nothing.
“People run them on 95 thinking they can get away with it. But 95 fuel here in New Zealand has proved to be inconsistent and sometimes dips below the 95 rating,” he said.
“To be safe, you need to be using 98 in these vehicles.”
Prevette said that 98-octane wasn’t available in all parts of New Zealand, and so Shelby NZ would sometimes tune its vehicles to be able to run safely on a lower octane.
“Most people who buy these things are buying them second-hand, and they don’t bother changing the tune,” he said.
“They bought an expensive truck, and the thing should still be going, but unfortunately it’s not.”
A spokesperson for 4 Guys said it would let the tribunal’s decision speak for itself.
Harrison and Neil are pursuing a further claim against Shelby NZ through the courts.
Jeremy Wilkinson is an Open Justice reporter based in Manawatū, covering courts and justice issues with an interest in tribunals. He has been a journalist for nearly a decade and has worked for NZME since 2022.
