A gun car is a feature in Grand Theft Auto IV and its downloadable contents, The Lost and Damned and The Ballad of Gay Tony, that allows the player to purchase weapons and body armor from the back of a road vehicle in an isolated location in the city. The feature complements unnamed gun dealers dotted throughout the city (which is an easier-to-access but more expensive option), and is intertwined with the games' friendship system.
Access to gun cars are possible to the player as soon as they are granted the ability to organize outings with a friend who specializes in selling weapons. Once the player manages to sufficiently increase their friend's liking towards the player, the player will unlock the ability to request for a gun car via their mobile phone; they are notified of this via a phone call from the aforementioned friend, informing that they can now call for weapons.
Once unlocked, a gun car can be called in by selecting the friend's name on the mobile phone's Phonebook, followed by "Gun Car". The player character verbally requests for the gun car, and the friend responds by notifying where they will be waiting for the player. The game then marks the location of the gun car on the map, to which point the player may proceed to the gun car. often times, the meetup point is located in an isolated location such as an alleyway or vacant land, illustrating the covert nature of the business. It should be noted that the friend will only wait for the player for several in-game hours before they decide to leave; there is however no penalty imposed on their friendship for this.
Upon arrival at the gun car, the player may interact with the friend in order to access the selection of items available for purchase. Much like regular gun shops, the player must pay more for a replacement firearm, but pay less if they simply wish to buy additional ammunition for a firearm in hand. The range of items on offer will also be expanded only after the player progresses in the storyline, preventing the player from acquiring overpowered firepower early in the game.
Once the player completes their purchase, the friend leaves with their gun car.