When buying a car, "OAC" means "on approved credit." A person seeking to finance the purchase of an automobile needs to meet a minimum credit score and associated credit history to obtain a loan.
Provided the minimum requirement is met in regard to a credit score and history, a person seeking automobile financing oftentimes is able to obtain a more favorable interest rate on a loan with a better credit track record. In addition, a prospective buyer's income is likely to be part of the on approved credit equation. OAC is prevalent in situations in which an automobile dealer finances the sale.