At yesterday's court appearance, Judge Barbara Morris sentenced the teenager to two months' community detention, in what she described as an "unusual move".
The charge of attempted arson carries a maximum sentence of 10 years' imprisonment.
Murphy's lawyer, Susie Barnes, said the teen had turned his life around since being sentenced in April to four months' community detention and nine months' supervision on other charges relating to the incident at the service station.
"I'm pleased to be able to describe this as a good news story, really.
"I hope that this is one of those cases that we rarely see where there's a turnaround in someone's fortunes."
Ms Barnes said Murphy was now working, had stopped drinking, had made new friends and was playing rugby.
"His life is just easier and better and he says the smell of alcohol makes him sick."
The judge said it was a serious crime as there was a "huge risk" the station could have caught fire.
But "in light of the steps that have been taken - and the turnaround - a sentence that might otherwise seem inadequate is appropriate".
"Normally the only thing the court has to deal with is how long the prison sentence is -- especially in the case of a petrol station with the large amount of flammable material that was there."
Murphy had been on a downhill track since the death of a friend in a high-profile crash, but was on a new path now, Judge Morris said.
"If you are going along that track, that should not be destroyed by sending you to prison.
"You've turned your life around and done everything that you have said you would, and the community wouldn't be served well by a custodial sentence."
