(CNN) Olivia Newton-John could never have envisioned "those summer nights" continuing for decades.
"I'm not a fortune teller," Newton-John told CNN. "I don't think anyone could have imagined a movie would go on almost 40 years and would still be popular and people would still be talking to me about it all the time and loving it. It's just one of those movies. I'm very lucky to have been a part of it. It's given so many people pleasure."
The four-time Grammy-award winner gained international fame in 1978, when she starred alongside John Travolta as Sandy in the movie musical, "Grease."
Her iconic high-waisted black leather pants? Newton-John still owns them but not for much longer.
The breast cancer survivor plans to auction the costume next year to benefit The Olivia Newton-John Cancer Wellness Research Center in Melbourne, Australia.
As for whether she'd inch the pants back on for the film's rumored 40th anniversary reunion next year?
"I'm not answering that question on grounds of incrimination," Newton-John responded with a laugh. "No, I will not put them on again."
Although she said nothing is officially planned yet to mark the film's milestone, Newton-John pays tribute to "Grease" during her concerts.
"It's expected!" Newton-John said of performing songs from the film's soundtrack. "I do four songs from the movie and the rest of the show is my other life. I've had many lives in music. I've had country when when I started, then I crossed over into pop. I had 'Xanadu' and 'Grease,' many songs in between. I feel very grateful. I have such a large repertoire to choose from."
But Newton-John acknowledges there's something special about "Grease" and the recent resurgence of onscreen musicals. Last year's "Grease" live TV special starring Julianne Hough was a ratings hit for Fox.
"I think it's wonderful, I love musicals," she said. "I loved 'La La Land,' thought it was wonderful and redoing 'Grease' was really fun, I enjoyed it. I thought Julianne [Hough] did a great job."
Currently on a North American tour with her new album "Liv On," Newton-John said her fans draw her back to the stage.
"I love to sing, it's all I know how to do," she said. "That's all I've ever done since I was 15, so it's my life. I feel very grateful that I can still do it and people still come to see me. I wouldn't be doing it if that wasn't the case, so I feel very lucky."