There is cheating, cheatin’ and creative interpretation of the rules.
Cheating is clear breaking of the rules including having a driver deliberately crash per Nelson Piquet Jr.in 2008. Deliberate use of illegal parts or oversize engines is real cheating.
Today a lot of ‘cheatin’ as the NASCAR boys call it in their series’ is inadvertent. Almost every Sprint Cup race somebody gets caught. NASCAR’s rule book has so many restrictions that people sometimes just make an honest mistake. There have been several cases where the parts supplied to a team by a respected supplier were inadvertently illegal. There is also no doubt a lot is deliberate. It has always been almost a game with the stock car crews trying to outsmart the tech. boys. That is one reason NASCAR several years ago appointed a former crew chief as chief tech. He was well known for ‘bending’ the rules.
One neat trick that got caught was running the fuel line through the rollcage tubes. Now they have strict rules on tank size and fuel line diameter. The fuel line duly entered the tube and a line came out in the engine bay. But there was no line in the tube! Extra fuel on board. The late Smokey Yunnick was the bane of the tech. people. Once he was getting better mileage than anyone and NASCAR knew he had to be cheatin’. They tore the car apart but found nothing. They kept at it until Smokey blew up. This was at Daytona and his shop was just across from the track. So he got in the car and fired it up and drove out of the track to his shop. Trouble was the gas tank was still sitting in the inspection bay!