Keselowski had just enough fuel remaining to hold off Denny Hamlin down the stretch at Charlotte, where track temperatures reached 120 degrees.
The Penske Racing driver didn't pit during the final 73 laps, enabling him to take the lead on lap 143 and hold it the rest of the way, claiming his 18th career Nationwide crown and second at Charlotte.
Hamlin shook off a balky carburetor to complete a strong second-place run, ending 0.8 seconds behind Keselowski.
Justin Bieber crashes Drake Bell's album release party
Putin thinks Obama would save him if he were drowning