What kind of gas does a 2018 Dodge Journey take?

Depending on configuration, Your 2018 Dodge Journey may or may not be Flex Fuel compatible. Specifically, the 2.4L 4Cylinder engine requires unleaded gasoline with an octane of 87 or higher, whereas the larger 3.6L V6 engine requires the same, or E-85 flexible fuel. Though You'll save at the pump with the later, reduced fuel mileage will largely mitigate this effect. As for premium gasoline, You can skip it -- research shows that it's only beneficial in engines with a high compression ratio, which the Odyssey does not have. You'll spend extra money at the pump for no additional benefits. While it won't exactly harm Your engine, there's no point in using it, as it's been repeatedly shown to be ineffective unless Your engine specifically calls for it.