McDowell beat Gaughan by 0.534 seconds on an overcast, sometimes misty afternoon at the sprawling road course. The Richard Childress Racing teammates went bumper-to-bumper midway through the last lap before McDowell held on at the finish line.
A regular on NASCAR's top Sprint Cup circuit, McDowell took his first career Xfinity checkered flag.
Three cautions in a late eight-lap stretch led to several bumps and spin-outs in the field around the 14-turn course. The extra time had crew chiefs fretting about fuel strategy.
McDowell had more than enough, spinning his wheels into a wall at the finish line to burn his tires in a smoky celebration.
Brennan Poole finished third.
