The type of gas you'll need to put in to your 2018 dodge durango will depend on which trim level you have. the base model, gt, sxt, and platinum will only run perfectly fine on regular unleaded gasoline with an octane of 87. the r/t and srt editions will have different motors and different fuel needs so they will need to run on premium fuel with at least 91 octane but preferably 93 octane. no matter which model you have they will all have a fuel tank capacity of 24.6 us gallons so you shouldn't need to be stopping for gas too often in this vehicle.
The durango gt, sxt citadel and anodized platinum are all able to use regular unleaded gasoline. the 2018 dodge durango r/t and durango srt are recommended to premium gasoline only.
I have the durango citadel platinum with the 5.7 hemi. on the gas door it says mid grade or higher and it also says the same thing in the owners manual. regular fuel is not recommended. i guess it depends on the model you have.