Out of gas is a common phrase used to describe a vehicle or equipment that has run out of fuel. However, the antonyms for this phrase can be as follows, fueled up, topped off, refueled, and fully gassed up. These words imply that the vehicle, equipment or machinery is in good condition and has enough fuel to operate efficiently. Essentially, ensuring that everything is fueled up, topped off, or fully gassed up, will prevent an individual from being stranded while on the road or unable to accomplish a task due to a lack of fuel. Hence, it is essential to check and maintain the fuel level to avoid the state of "outta gas".