Deductions & credits

It depends on whether or not you are in the business of renting vehicles or not. 

• If you are, the income and expenses go on Schedule C - Where do I enter Schedule C?  
• If you are not, the income goes to miscellaneous income - Income from renting out personal property.

Miscellaneous Income (non-business) can be found by going to Federal > Personal Income (Wages & Income) > Less Common Income > Miscellaneous income, 1099-A, 1099-C > Income from renting out personal property.  

See IRS Topic 414 - Rental Income