Most lending for car purchase is 'unsecured' - fixed-rate loans that are not 'secured' by a charge over something of value (e.g. property or the car itself) to protect the lender if the borrower defaults on the repayments. This is why credit checks are such an important part of the loan application process.
Lenders who offer 'secured' loans usually restrict them to homeowners; equity in the property forms the security. Secured loans allow you to borrow larger sums at lower (and sometimes floating) rates of interest - but you need to be confident that you can keep up the repayments.
See also REMORTAGING