Lubel has led CST—one of the largest independent fuel retailers and convenience-store operators, with $10.8 billion in sales—since its 2013 spinoff from Valero Energy, where she was EVP and general counsel. She’s been on an acquisition tear, doubling the Fortune 500 company’s reach in fuel distribution. Last year CST sold 2.9 billion gallons of fuel to the public in the U.S. and Canada.

For more on newcomers and returns to the list, read “Who’s on? Who’s off? Fortune’s list of the Most Powerful Women has plenty of changes.”