Nitrous oxide, also known as Nitro (N2O), is a chemical compound often used to boost the speed and acceleration of a vehicle in Grand Theft Auto: San Andreas, The Ballad of Gay Tony and Grand Theft Auto V.
GTA San Andreas
In GTA San Andreas, nitrous is a reusable vehicle component that can be installed on modifiable vehicles at any mod garages in San Andreas. Nitro comes in three "sizes"; 2x, 5x, and 10x. Each boost is identical, however the number of uses is limited. 2x allows 2 nitrous boosts before running out, 5x allows 5, and 10x allows 10.
Nitrous serves to dramatically increase the torque (and thus power) of a car. Thus, it boosts a vehicle's acceleration quite noticeably, however, does not increase top speed. Using it on rear-wheel drive cars may cause immense oversteer, and on front- and all-wheel drive cars may cause understeer. Cars will almost universally wheelspin when flooring the gas from a standing start with nitrous, save for the most underpowered of vehicles such as the Romero and Perennial. It is most efficiently used to assist in acceleration after a crash, from a standing start, or out of a corner in a windy road, as it does not boost a vehicle's top speed.
When installed on a vehicle, the "fire" button can be pressed to activate a nitrous boost. The boost increases the speed and acceleration of the vehicle dramatically, with exaggerated motion blur and bright blue flames spewing out of the exhaust pipe(s), before the nitrous exhaust ceases after a given period of time.
Each depletion of nitrous is followed by a delay period when the nitrous tank "refills" and the player will not be able to use another boost right away. Players will be able to identify this by keeping tabs at the exhaust pipe(s), which will emit blue fumes while the nitrous refills. When the fumes no longer appear (releasing normal exhaust smoke instead), the player is allowed to use the nitrous again. An exploit exists that allows players to regain use of nitrous faster by simply exiting the car that is refilling its nitrous tank and immediately reentering it, thereby resetting the status of the nitrous tank and refilling the nitrous instantaneously.
Players must be careful not to abuse the nitrous. Using nitrous near a police officer triggers a one-star wanted level.
The Ballad of Gay Tony
In The Ballad of Gay Tony, nitrous is limited to use in Triathlons and multiplayer races, although the boost can be controlled. Motorcycles in Race and GTA Race multiplayer modes are also equipped with nitrous, but are often very risky to use as collisions while riding a nitrous-boosted bike are potentially fatal. Even vehicles like the APC may also be equipped with nitrous in such races.
Much like in Need for Speed and other similar games, a small tank-shaped bar next to the radar will show the amount of nitrous available, which will regenerate in time. When the nitrous amount reaches over the 45% mark, the player is ready to use the nitrous; in addition a high-pitched humming noise will be heard from the car, along with small orange fumes from the exhaust pipes. The player can continuously use the nitrous until it completely runs out, after which the player must wait until the bar refills to at least the aforementioned 45% to use the nitrous again. Unlike in GTA San Andreas, the nitrous in TBOGT can instantly catapult a vehicle to its top speed (or close to it), and the dramatic boost in speed may be shocking if the player's vehicle is traveling at a lower speed.
Nitrous boosts can also provide players a head start in races; this is accomplished by spinning the car's tires at the starting line (by holding the accelerator and brake/e-brake commands simultaneously), and activating the nitrous and releasing the brakes at the same time when the race starts. If done correctly, the car will attain a massive boost in speed that will easily propel it into the lead. This trick does not work in APC races.
Nitrous was featured to Grand Theft Auto V but was cut from the game before release for unknown reasons. Before the 1.11 update it was possible to add it to vehicles through editors and save editors though is no longer useable unless all patches after 1.10 are removed.
It worked similar to The Ballad of Gay Tony's nitrous system; it re-charged as you drove, but there was only one useable boost at a time, after that it would recharged slowly. Unlike TBoGT, you could use the boost again before its fully recharged but there was no way to tell how much boost you had as there is no meter on the screen to indicate.
A nitrous oxide tank can be seen inside the Duke O'Death in the enhanced version of GTA V, however, it serves no function besides a visual one. This can also be seen in various other high-end muscle cars, such as the Blade and Dukes.
In the Heists Update of Grand Theft Auto Online, the motorbike Lectro has a Special Ability called KERS which works like Nitro of older games. This also applies for the Vindicator bike, which also has the KERS feature from the Ill-Gotten Gains Part 2 update.