GM offers the 2015 Buick Regal in four distinct trim levels: base, Premium I, Premium II and GS. All Regals come standard with a turbocharged 2.0L 4-cylinder that produces 259 horsepower and 295 ft-lb of torque. An optional 2.4L 4-cylinder with eAssist light hybrid technology is also available, delivering 182 horsepower and 25 mpg in the city, 36 mpg on the highway. Front-wheel drive is standard on the Regal, though all-wheel drive is available on all trims. A 6-speed automatic transmission with Driver Shift Control is standard, though the performance-oriented Regal GS can be optioned with a 6-speed manual. The eAssist model is a light hybrid, meaning its electrical system enhances acceleration as well as saving fuel. With the Regal, the battery pack and electric motor are good for 15 horsepower and 79 lb-ft of torque on demand. The energy isn't stored like in typical hybrids-- rather, it's constantly generated, thanks to regenerative braking, and used as needed. The system works quite subtly in the background, so drivers who don't already know about the system won't even notice it working. On the outside, the Regal has a curvy, aggressive and performance-oriented look and that carries over to the inside, where the Regal includes, high-quality materials, firmly bolstered sport seats and has an instrument panel that flows uninterrupted through to the door panels. Ice-blue lighting and a thick-rim steering wheel set a sportier mood than that of Buicks of the recent past. Among the safety features included with all Regal models are electronic stability control, 4-wheel anti-lock brakes with Intelligent Brake Assist, six airbags, StabiliTrak electronic stability control, traction control and a rearview camera system. The Regal's stiff body structure enhances safety while helping with ride and handling. Buick's QuietTuning technology ensures the Regal provides one of the quietest rides in the segment. Standard features on the Regal are generous, and include 18-inch alloy wheels, a power driver's seat, heated front seats, leather upholstery, a Bluetooth hands-free system, XM satellite radio and the OnStar security and assistance system. Premium I and II trims include luxuries such as a power passenger's seat, push-button start, ultrasonic rear parking assist, a heated steering wheel, HID headlights, rear thorax airbags and a premium Bose audio system. The top-of-the-line Regal GS adds 19-inch alloys, an 8-inch driver information display, Brembo brakes and improved suspension, unique exterior body trim and Interactive Drive Control, which integrates the stability control system with electronically controlled dampers, to allow a soft, comfortable ride when cruising but tighten up the suspension within milliseconds when needed for emergency maneuvers. Top options on the Regal include a navigation system, along with several new advanced safety technologies such as forward collision alert, blind spot alert, lane departure warning, adaptive cruise control and rear cross traffic alert.