The disadvantage of a vehicle-secured loan is that you need to have the car fully paid off and in your name. And we know that for many Brazilians, financing a car is the reality. In these cases, it's not possible to apply because the car is tied to the financing bank. In other words, it's not yet truly yours. 

Furthermore, even if you are married and the car or motorcycle is registered in your spouse's name, it is not possible to apply for a secured loan in your name. 

It's also important to point out that, although you can still use the vehicle, it remains pledged to the bank. Therefore, it cannot be transferred to another person's name or sold until the debt is paid off. Again, the car "belongs" to the financial institution granting the loan. After all, they need the guarantee in case you fail to meet your financial obligations. 

Even if you have a good credit profile and a fully paid-off car in perfect condition, the financial institution is not obligated to offer you a loan secured by your vehicle. Credit approval is at the discretion of each institution. 

Finally, a vehicle-secured loan is much more bureaucratic than applying for a personal loan, for example. After all, it is necessary to have the vehicle inspected, as it is subject to lien and you are liable to lose the asset in case of non-payment. 

Finally, even if you own a car, if it's very old, you risk not getting the loan. This is because many banks don't accept vehicles that are more than 15 years old from the date of application.