Dodge 2009 Dakota - Manual (Page 308)

CAUTION!
Replacing fuel system components with non-ethanol
compatible components can damage your vehicle.
ADDING FUEL
Fuel Filler Cap (Gas Cap)
The gas cap is located behind the fuel filler door. When
fueling, the cap may be placed on the inside of the filler
door.
If the gas cap is lost or damaged, be sure the replacement
cap is for use with this vehicle.
Gas Cap Holder
306 STARTING AND OPERATING