All gasoline sold in the United States is required to contain effective detergent additives. Use of additional detergents or other additives is not needed under normal conditions and would result in additional cost. Therefore you should not have to add anything to the fuel.
See also:
Vehicle Identification Number
The Vehicle Identification Number (VIN) is found on the left front corner of
the instrument panel, visible through the windshield. This number also appears engraved
on the right front door sill un ...
Battery
The battery is of the “Limited maintenance” type: under normal conditions of
use the electrolyte does not need topping up with distilled water. ...
Wing window
IMPORTANT
Open and close the wing window only when the vehicle is stationary.
The Fiat Doblò may fit a handy wing window on the roof on the back of the load
compartment to carry long object ...