The Regal name first appeared on Buick products during the 1973 model year attached to mid-sized vehicles. In 1998, the Regal shared a platform and exterior appearance with the lower-end Buick Century. The most notable characteristic setting the Regal apart from the Century was five-passenger seating as opposed to six. The Buick Regal was offered in LS and GS trim levels from 1998 to 2004. All models of the sedan included standard air conditioning, AM/FM cassette stereo and remote keyless entry. The 1998 Buick Regal received power from a naturally aspirated and supercharged version of a 3.8-liter Series II V-6 engine. The Regal GS was standard equipped with the 240-horsepower supercharged engine. In addition to producing stout performance, the GS model also allowed the Buick sedan to achieve highway fuel economy of 27 miles per gallon. From 2000 to 2004, Buick collaborated with fashion designer Joseph Abboud in producing a special appearance package version of the Regal. Joseph Abboud editions of the Buick Regal featured the use two-tone coloring and included 16-inch wheels. In 2005, Buick replaced the Regal nameplate of their mid-sized sedan with LaCrosse. With the LaCrosse moving up Buicks model range to be a flagship vehicle, the Regal name was revived in 2011. Derived heavily from the European Opel Insignia, the 2011 Regals European flair was combined with a 182-horsepower 2.4-liter Ecotec engine and a 220-horsepower turbocharged 2.0-liter powerplant. A year after introduction, the Buick Regal line added a performance-driven 270-horsepower GS model. In 2013, eAssist was added to the Buick Regal allowing the engine to temporarily shut off to save fuel when the vehicle is at a standstill.