Boommobile
Artifact — Vehicle
When this Vehicle enters, add four mana of any one color. Spend this mana only to activate abilities.
Exhaust — 
: This Vehicle deals X damage to any target. Put a +1/+1 counter on this Vehicle. (Activate each exhaust ability only once.)
Crew 2
Ian Jepson
Aetherdrift (DFT)
• #310Rulings
Exhaust abilities can be activated any time you could normally activate an ability.
(wotc • 2025-02-07)
You may spend the four mana added by the first ability on the same ability or on multiple abilities.
(wotc • 2025-02-07)
If an exhaust ability of a permanent is activated, and then that permanent leaves the battlefield and returns to the battlefield, it becomes a new object so its exhaust ability can be activated again.
(wotc • 2025-02-07)
If an ability triggers whenever you activate an exhaust ability, that ability resolves before the exhaust ability resolves.
(wotc • 2025-02-07)
Rulings
Exhaust abilities can be activated any time you could normally activate an ability.
(wotc • 2025-02-07)
You may spend the four mana added by the first ability on the same ability or on multiple abilities.
(wotc • 2025-02-07)
If an exhaust ability of a permanent is activated, and then that permanent leaves the battlefield and returns to the battlefield, it becomes a new object so its exhaust ability can be activated again.
(wotc • 2025-02-07)
If an ability triggers whenever you activate an exhaust ability, that ability resolves before the exhaust ability resolves.
(wotc • 2025-02-07)