It took a radio disc jockey to remind Jay Leno where he’ll stand in Tonight Show history when he walks off the stage for the last time on Friday.

Leno was at the wheel of one of his famous vintage cars when he heard the DJ conduct a pop quiz: Who’s the second-longest-running host of Tonight, after Johnny Carson?

“The guy on the radio actually got it before I did,” Leno said on Thursday, smiling. “It just sort of made me laugh. I went, ‘Oh, that’s pretty good’.” Maybe even better than good?

“I come from ‘pretty good’,” replied Leno, unfailingly modest in interviews. “If somebody wants to say even better, that’s great.”

He will have posted an impressive 17 years as Tonight host, but well short of Carson's three decades that ended with his retirement in May 1992. Leno debuted as Tonight host a few days later.

He leaves the show atop the late-night ratings, his run abbreviated by NBC's decision five years ago to create a succession plan that gives Tonight to Conan O'Brien.

Leno moves to a new, untested 10 pm daily prime-time show for NBC this fall.