The Lexus IS remains offered in two different body styles, both available in IS 250 or IS 350 guise. IS 250 models come with a 204-horsepower, 2.5-liter V6 engine while IS 350 models get a 306-hp, 3.5-liter V6. Both engines come with variable valve timing for responsiveness as well as fuel efficiency--the IS 250 is quite economical with EPA ratings of up to 21 mpg city and 29 highway. While the IS 250 comes standard with a 6-speed manual transmission, with a 6-speed automatic (and steering-wheel paddle-shifters) optional, all IS 350 models come with the automatic. In all Lexus IS models, a double-wishbone suspension design in front and a multi-link rear setup help reduce weight and increase responsiveness. The suspension in the IS is tuned to be quite firm, yet there's enough give to maintain enough ride comfort for most. The IS has rather compact exterior proportions, which means that backseat space is tight for the tallest adults, especially in IS C convertibles. However it's quite comfortable in front. Leather upholstery is standard, with new black-metallic accents in the sedan and the IS sedan has a reasonably large trunk. Although the Lexus IS C convertibles bear a strong likeness to the IS sedans from the front and back, their fast-opening retractable hardtop setup, made of lightweight aluminum, is an excellent way to enjoy open-air motoring without compromises the rest of the year. The top opens or closes in just 20 seconds and wind buffeting is quite good with it down. A full roster of airbags is of course standard, but IS models also include anti-lock brakes and Brake Assist, an advanced electronic stability control system called VDIM. It incorporates the electric power steering to help maintain control in an emergency maneuver. Standard features on the IS include power front seats, dual-zone climate control, rear seat vents, a power moonroof, a telescoping steering wheel, a HomeLink universal remote and an auto-dimming rearview mirror. Also standard is a premium audio system with 13 speakers, Bluetooth hands-free calling and audio streaming, satellite radio and a CD changer. The IS 250 AWD and IS 350 AWD add heated seats. Options across the lineup include a navigation system that incorporates a Mark Levinson premium surround sound system, which has 14 speakers and 300 watts. The Lexus Enform with Safety Connect feature is an extra for the navigation system, bringing direct emergency operator-assisted service as well as access to information from XM's NavTraffic, NavWeather and Sports and Stocks services. HID headlamps and LED running lamps are available on the IS 250 sedan and standard on the IS 350, while other high-tech options include rain-sensing wipers and radar cruise control with a Pre-Collision System. The available navigation system includes a rear backup camera; another option is Intuitive Park Assist, which employs ultrasonic sensors to indicate proximity to other vehicles. A performance-oriented IS F sedan stands at the top of the IS lineup; it gets an 8-speed Sport Direct-Shift transmission with paddle shifters plus Brembo disc brakes, 19-inch wheels and a performance suspension--plus a 416-horsepower, 5.0-liter V-8 engine. Altogether, the IS F can get to 60 mph in just 4.6 seconds, according to Lexus. New for 2011 is an F Sport Package for rear-wheel drive models; it adds many of the features of the IS F, including a sport suspension and special steering tuning, along with dark-finish 18-inch wheels, front and rear spoilers and an Ultrasonic Blue exterior hue. A set of F Sport accessories, available at dealerships for both on the sedans and convertibles, adds many of the appearance upgrades individually.