"Thievery?" he repeated with mock offense. "Perish the thought. Sirius has a car. And Sirius is out of town. Ipso facto, I've got a car."
He wasn't intending to imply that he owned the thing in any way, but he certainly had access to it. If it were him with the car and off on vacation, he'd let Sirius use it. What was the worst that could happen? Apart from the obvious when it came to a contraption that relied on explosions to move itself. Probably something about gas. And how James could rarely recall how to tell when you needed to more in.
Besides, Amarissa here appeared to be rather qualified. Handy thing, having a muggle parent when it came to automobiles. And obscure things like airplanes. Airplanes were ridiculous, but James sure as hell wanted to try one. But they probably didn't let just anyone fly those things.
"You know, if you think I'm just beyond hope... you could drive," he suggested with a wry smirk.