He doesn't mean it, it just tends to happen because he keeps thinking without realising he's still staring.

"Well, if you mean the whole car. Two years, but only because well, Hogwarts doesn't really have shop class. But I've been working on installing the engine since... Sunday night? Well not just the engine, I was checking wiring, clearing out pipes. You'd be surprised how dirty things get when you only come home a few times a year to maintain things. And re clean the part of the engine I didn't take to Hogwarts this year."

Without paying any attention to the decorated but obviously unused surrounds, Tony leads her back to the theatre room, where he knows there's drinks.