just to be the odd one here since everyone is going on about either liquid combustible fuel or fusion. what about fission? one would assume that if Bruce could travel through time/dimensions he would have found a way to utilize fission without all the steam punk currently used. even without breaking space/time there have been efforts to do just that as early as the 1950's. and given that a
boy scout in a garden shed can build a fission reactor small enough to fit in the trunk of his car one would assume the Morrow Project with far greater resources would be able to produce a lightweight nuclear fission power plant for their vehicles. (Ford managed to in
1958 after all.)