The BMW X5 is a luxury crossover SUV introduced in 1999. It was BMW's first SUV (Sport Utility Vehicle) also known as "Four-by-Four" (4x4) in the UK. It features all-wheel drive and is available with either manual or automatic transmission (the manual transmission option was dropped from the 2006 model year onwards). A range of gasoline inline-6s, V8s and diesel engines are offered. BMW describes the X5 as a Sport Activity Vehicle (SAV) rather than an SUV, to emphasize its on-road ability despite its size. Like the Lexus RX 300 and Mercedes M-Class, the X5 heralded the shift from truck-based body-on-frame SUVs to sedan-based crossovers that would come to fruition in the late 2000s.