Is a 4% difference between the profit rate of savings certificates (13%) and the car installment rate to the showroom (9%) considered usury?

It is not permissible to purchase a car through a bank unless the following conditions are met: 1. The bank buys the car for itself before selling it to the client. 2. The bank takes possession of the car before selling it to the client, based on the Prophet's (peace be upon him) saying: "If you buy something, do not sell it until you take possession of it." 3. The ownership of the car transfers to the buyer upon the conclusion of the contract. There is no objection to mortgaging it or restricting its disposal until the installments are paid, but it is not permissible to make the transfer of ownership contingent upon the payment of installments. 4. The contract must be free of any penalty clause for late payment. 5. The contract must be free of the condition of comprehensive insurance if it is commercial.

As for savings certificates with a return as a percentage of the capital, these are usurious certificates that are absolutely forbidden to deal with. If the car purchase contract is valid and the client dealt with usurious certificates, then they have fallen into usury to pay the installments. If the contract itself is forbidden, then they have combined two forbidden transactions. It is permissible to benefit from a permissible investment to pay the installments.