Phoenix is the default vehicle in RAGE 2. You get it at the beginning of the game.
Phoenix can be upgraded to make it even better for exploration and combat. This page focuses on the following upgrades:
Gatling Guns - weapons mounted on the vehicle's hood.
Safe Mode - increases the vehicle's durability.
Blast - an energy beam that deactivates nearby shields.
Cruise Missile - targets and shoots the enemies automatically.
Reinforced Armor - increases the vehicle's durability.
Ejector Seat - leave the vehicle instantly.
20MM Cannons - another weapon for your vehicle.
Hellfire Mortar - its projectiles target enemies automatically.
Nanotrite Skin - another upgrade that increases the vehicle's durability.
The upgrades aren't mutually exclusive. You can buy them all to make your vehicle practically indestructible.