A neighbour saw the car burst into flames seconds after he walked away from it.
The duo was arrested on a car park in Ashton-on-Ribble. Nightingale still had the Audi car key in his possession, and forensic tests on a window sill at the house found a print that matched his footwear.
Defending, Anna Chestnutt said Nightingale had not offended for five years. She said he was giving his partner Holmes, who has mental health problems, round the clock care but became overwhelmed with his caring responsibilities.
He had relapsed into drug and alcohol use and made a foolish decision.