1
general::
Phrase(s): gas up
to fill up one’s gasoline tank with gasoline. • I have to stop at the next service station and gas up. • The next time you gas up, try some of the gasoline with alcohol in it., Phrase(s): gas something up
to put gasoline into a vehicle. • I have to gas this car up soon. • I will stop and gas up the car at the next little town.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
Supply a vehicle with gasoline, as in I want to be sure to gas up before we go. James M. Cain used this term in The Postman Always Rings Twice (1934): "I went to gas up a car." [Colloquial; c. 1930] Also see TANK UP.
American Heritage Idioms