The 2021 Mustang is available as a fastback or as convertible, with one of four engines. The base engine is an EcoBoost 2.3L turbocharged 4-cylinder. More powerful Mustang GT variants are powered by a 5.0L V8. The top-of-the-line engine is a 5.2L V8 powering GT350 and GT500 models. The EcoBoost makes 310-330 horsepower and 350 lb-ft of torque, while the V8 engine in the GT makes 460 horsepower and 420 lb-ft. The GT350 is rated at 526 horsepower and 429 lb-ft while the beastly GT500 produces a whopping 760 horsepower and 625 lb-ft of torque mated to a seven-speed dual clutch automatic transmission. In other words, the Mustang is fast in all of its forms. All vehicles can be mated to either a standard 6-speed manual or a 10-speed automatic transmission minus the Shelby variants. Adjustable driving modes such as Normal, Snow/Wet, Sport and Track allow drivers to custom-tune the responsiveness of the Mustang to the task at hand. Fuel economy on the EcoBoost is rated at 21 mpg in the city and 31 mpg on the highway, while the 5.0 V8 returns 15 mpg and 25 mpg, respectively. There are several trim levels for the fastback: EcoBoost and EcoBoost Premium, GT and GT Premium, GT500 GT350 and GT350R. The convertibles simplify things by only offering EcoBoost, EcoBoost Premium and GT Premium trims. The EcoBoost Mustang's standard equipment includes 18-inch wheels, a 4-way manual adjustable driver's seat, 50/50 split-folding rear seat, a 6-speaker sound system, the SYNC 3 infotainment system, active noise cancellation and an "intelligent" key. The Ecoboost handling package adds MagneRide suspension, an upgraded Limited slip differential, stiffer spring rates, a thicker rear sway bar, and 265mm Pirelli P Zero tires. The EcoBoost Premium trim adds dual-zone automatic climate control, heated mirrors, additional exterior lighting, heated and cooled leather front seats with six-way power-adjustability for the driver, and a 9-speaker stereo with SiriusXM satellite radio compatibility. The Mustang GT and GT Premium come similarly equipped to the EcoBoost trims, though of course GT models are powered by the fire-breathing 5.0 V8 engines rather than the fuel-sipping four-cylinder turbo. Several performance options and packages are available, including a range of rear axle ratios, several wheel choices, and Recaro sport seats. A California Special Package adds 19-inch ebony wheels, ebony suede seat inserts with red stitching, special door panel inserts, an aluminum dashboard finish and more. The Shelby GT350 and GT350R variants use a special flat-plane crankshaft that allows its big V8 engine to rev to over 8,000 rpm. It's a special engine, using technology normally found in high-end supercars. Usually, a larger V8 means lots of torque lower in the rev range, but a compromised ability to make power at higher rpm. With the Shelby GT350, there are no such compromises. The GT350 also has standard magnetic shocks, a more aggressive exterior package and various interior badges. Mustang packages include a Performance Package, for both the EcoBoost and GT. It offers a Torsen limited-slip differential, 19-inch wheels, an engine-turned aluminum instrument panel, gauge pack, heavy-duty front springs and larger brakes, a bigger radiator, and unique chassis tuning. The Pony Package adds different 19-inch wheels, unique upper grille and Pony logo, a side stripe and bright trim at the beltline and around the window. Finally, the Premium Plus Package upgrades Premium trim Mustangs with color-accented leather seats, a heated steering wheel, a 12-inch LCD digital display, a center console with hand stitching and more.