For support for minors, there is an obligation to provide shelter and its related costs, food (whether at home or providing an allowance for meals outside of the home, clothing, health care costs, possibly some nominal allowance to meet those needs not provided at home. I'd include travel costs to school (but not for vacations/parties), so that part of operating the vehicle and its related costs could be included in support. I would also include cost of a laptop/computer and internet access in support at this point too. Clearly, if the parents purchase a car for a 26 year old titled in the child's name, that is a completely different scenario.
Gifts would be contributions to UTMA, 529, IRAs; larger amounts not for support; a car; other expensive gifts not required for their health/well being.
Also, this is an older article on the subject of dependency of college students but still worth the read: https://www.thetaxadviser.com/issues/2010/aug/nichols-aug-2010.html