Epsilon is General Motors' mid-size front-wheel drive automobile platform. The architecture was multi-division project of GM North America, Opel and Saab, and debuted in the 2002 Opel Vectra and 2003 Saab 9-3. Since this platform falls squarely in the center of the worldwide automobile market, GM plans to produce a great many Epsilon vehicles with over a dozen variations. , it was GM's highest volume worldwide platform. Even after the dissolution of the GM/Fiat partnership, both companies retain the rights to continue developing Epsilon-derived models. A total of 16 different models have made use of the GM Epsilon platform, some of which remain in production 19 years after the platform debuted. Features GM's Epsilon platform replaced the N platform in the US, and replaced the GM2900 platform elsewhere. Vehicles of this platform generally carry the symbol "Z" in the fourth digit of their VINs. When the platform debuted, there was talk of an "Epsilon Wide" derivative, which was supposed to have provided the underpinnings for the Buick LaCrosse and Saab 9-5. However, the program was cancelled and the LaCrosse was put on the W platform, and the 9-5 was given a quick refresh for the 2006 model year. The Epsilon platform is a midsize front-driver promising a 200 percent improvement in rigidity, with aluminum suspension components—MacPherson struts in front and a four-link independent arrangement in the rear, and four-wheel disc brakes. Many of the Epsilon vehicles use the Ecotec Inline-four engines and both the High Value and High Feature V6 engines. The refreshed 2008 SAAB 9-3 debuted with an advanced version of all-wheel-drive it dubbed XWD, finally giving a definitive answer to rumors about the platform's ability to support AWD, which had been around since the debut of the platform. The Lambda and Theta Premium crossover platforms are derived from Epsilon. Vehicles Vehicles based on the Epsilon I platform: Regular 2002–2009 Opel Vectra C saloon and liftback 2002–2009 Vauxhall Vectra saloon and liftback 2002–2009 Holden Vectra 2002–2009 Chevrolet Vectra 2003–2011 Saab 9-3 2010–2012 Saab 9-5 2004–2007 Chevrolet Malibu 2006–2009 Cadillac BLS Extended 2002–2009 Opel Vectra C Caravan 2002–2009 Vauxhall Vectra Caravan 2003–2008 Opel Signum 2004–2007 Chevrolet Malibu Maxx hatchback 2008–2012 Chevrolet Malibu 2005–2010 Pontiac G6 2005–2011 Fiat Croma 2007–2010 Saturn Aura Cancelled vehicles which would have used this platform: 2006 midsized Buick Epsilon II A new version of the Epsilon, dubbed Epsilon II, debuted in 2008. It is adaptable for