Could the UFO's method of traveling be using ions that move through spacetime without loss (without drainage)?

I think they are partial to Lyft.

Well, once they break the gravitational field of their home planet they pretty much keep going without any power or loss of speed, until they fall into the gravitational field of another star or planet.

As far as anyone knows, maybe. Surely there’s more to it than that.

No, once it gets going, gets free from gravitational effects, it just keeps going and going. No slowing down, no speeding up. It doesn’t need any type of fuel, except when it’s landing, or perhaps to do a course correction.
That’s how Apollo 13 made it back from the moon. They had to conserve their fuel so they set their course and then shut everything dpwn. As Tom Hanks said, “We’ve just put Sir Issac Newton in the driver’s seat.”

I believe that they must manipulate spacetime. In regards to long distance methods of transportation.

I don’t see propulsion as a realistic way for organic aliens to travel. Unless they have extremely long lives, don’t care to have “generational” vessels, or somehow aren’t effected by inertia. Or if they’re machines…

Methods for propulsion inside an atmosphere, or for general maneuvering, could vary…