Beck Adam Renalson (20) later explained the incident was designed to send a message to the victim, that he was "crazy, dangerous and unexpected".
Renalson told police immediately afterwards that he had been ruminating about the crime for a while and he did it to "make a point not to f... with me".
He appeared in front of Judge David Robinson in the Dunedin District Court this week after pleading guilty to arson, breaching a protection order and breaching supervision.
Six months earlier, he came before the same judge in the same courthouse for contacting his ex-girlfriend in contravention of a court order.
On November 8 last year, Renalson was sentenced to nine months’ supervision on the basis he would be living away from Dunedin, had contacted mental-health services and had employment on the horizon.
"I had real hopes it was a blip," the judge said this week.
But it was not.
Late on November 13, Renalson set off from Oamaru with nearly four litres of petrol in a container.
He arrived at the victim’s home in the early hours of the morning.
As she slept just metres away, the defendant approached her car and poured the petrol into the engine bay through the vents on the bonnet.
Renalson set the vehicle alight then fled the scene.
By the time firefighters arrived, it was extensively damaged.
The court heard a wooden fence of an adjacent property was also aflame, and was doused by neighbours using a garden hose.
The episode had left the victim in "a constant state of fear", Judge Robinson said.
In a statement she detailed her lack of sleep, hyper-vigilance, depression and suicidal thoughts, which had been exacerbated by Renalson’s most recent acts.
Crown prosecutor Marcail Brosnan called the incident "highly premeditated" and the judge agreed.
In an interview before sentencing, Renalson talked about the relief and pleasure he experienced from causing harm to his ex-girlfriend.
Counsel John Westgate, though, told the court his client was describing how he felt at the time, rather than how he now felt.
"He’s not inherently evil or inherently dangerous," he said.
"He spent 155 days in jail [on remand] and had plenty of time to reflect, and has moved on."
Mr Westgate argued Renalson should be sentenced to home detention, which he could serve in Auckland.
But Judge Robinson said the need to deter the defendant from such future conduct and to protect the community was paramount.
The crimes, he said, were "calculated and determined, to cause maximum fear".
Renalson was jailed for two years and three months.
