Mixing Moon Patrol with a bit of Defender, Gas Hog has players monitoring a rapidly depleting gas gauge as they obliterate attacking aliens. Players maneuver their "GasHog" on the top half of a constantly side-scrolling screen, as flying saucers drop bombs and enemy ships attempt to collide with the vehicle. Well-timed jumps can be executed, by pressing "up" on the joystick, in order to avoid holes in the ground and low-flying enemies, or to shoot at higher flying enemies with the laser cannon. Falling through a hole and onto the lower half of the playfield causes the GasHog to reverse course, yet allow players to locate critical fuel modules. Points are scored by shooting down enemy ships and saucers and by colliding with random "point values." However, point values that are shot will be subtracted from the overall score.