Infiniti G25x is a midsize four-door sports sedan produced by Infiniti, the luxury vehicle division of Japanese automaker Nissan. It is part of the G series, which includes the G20, G35, G37 and other models. The G25x was first introduced in 2005 and is powered by a 2.5-liter V6 engine. It is available with either a five-speed automatic or six-speed manual transmission.