Agreement doesn't mean Written Agreement even the verbal conversation will bind the firm if it result in any agreement. And as far as your problem is concerned TDS will be deducted @2.06%or 2.266% if surcharge applicable u/s 194C of Income Tax Act.
26 June 2009
If the car is taken on rent with exclusive possession, i.e. the whole control on the car is exercised by the lessee, then Tax need to be deducted u/s 194I
However, if the car is not in exclusive possession of the person but controlled by the owner of the car then tax need to be deducted u/s 194C.
It is irrelevant whether you have a written agreement or oral one.