Spaceviews made an analysis of cold gas thrusters. Elon has previously said the roadster will use a SpaceX cold gas thruster system with ultra-high-pressure air in a composite over-wrapped pressure vessel in place of the 2 rear seats. The SpaceX option package for new Tesla Roadster will include ~10 small rocket thrusters arranged seamlessly around car. These rocket engines dramatically improve acceleration, top speed, braking & cornering. Maybe they will even allow a Tesla to fly

SpaceX cold gas thrusters will need to emit very roughly 28 Kg of compressed air every second to keep our Roadster hovering.

How much air the COPV might hold ? A COPV with hemispherical ends of very roughly 2.0 meters x 1.0 meter should fit. That would conveniently have a volume of a bit more than one cubic meter. In 2021, Elon has said around 10,000 PSI. Air at a pressure of 10,000 PSI has a density of at least 500 Kg per cubic meter (depending on temperature). This sounds a lot, but is around a quarter of the mass of the whole car, so it seems feasible. This would enable a hovering time of about 20 seconds.