The car is considered personal no matter how often you use it in your business. It is not in the S-Corps name. Therefore, any credits or loan liabilities are personal and should not be reported as a S-corp asset.
You can have the S-Corp reimburse you for the business percentage use of the vehicle under the actual expense method if you chose to pay all the car expenses.
You can also have the S-Corp pay some of the car expenses and classify it on the Form 1120-S as a loan or an advance to you.
The key is to retain meticulous records and keep mileage logs in case of an audit.
