Keselowski was cited after flunking a post-race inspection Sunday at Dover International Speedway, when the sanctioning body determined the front end of his car was too low.
The Penske Racing driver finished fifth at the 400-mile event.
The sanctions dropped him from eighth to 10th in the Sprint Cup standings. He fell to just eight points ahead of 11th-place Jeff Gordon.
Crew chief Paul Wolfe was assessed a $25,000 fine and put on probation until Dec. 31, while team owner Roger Penske was penalized six car-owner points.
Penske Racing said in a statement "the problem is being addressed internally to ensure it does not occur again and the team is not planning to appeal the penalty."
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