Sleek styling, a high-class interior and plenty of performance combine to make the 2013 BMW Z4 a highly desirable roadster. Its new base engine for this year makes it even better. Powerful six-cylinder and efficient four-cylinder engines; quick-folding hardtop; comfortable ride; big trunk (with the top raised); excellent visibility for a roadster. The 2013 BMW Z4 introduces a new entry-level model. Replacing the sDrive30i and its normally aspirated six-cylinder engine is the new sDrive28i with a turbocharged four-cylinder. The new engine produces more torque than the former six-cylinder, and when it's paired with the standard six-speed manual transmission, a stop/start system delivers surprising fuel efficiency. The 2013 BMW Z4 is a two-seat convertible with a retractable hardtop, available in three trim levels that correspond to engine choice: sDrive28i, sDrive35i and sDrive35is. The 2013 BMW Z4 sDrive28i is powered by a turbocharged 2.0-liter inline-4 that produces 240 hp and 260 lb-ft of torque. Rear-wheel drive and a six-speed manual transmission are standard, while an eight-speed automatic is optional. In Edmunds performance testing, a manual-equipped 28i went from zero to 60 mph in a respectably quick 5.8 seconds. Manual-equipped cars include an automatic stop/start function that turns off the engine when the car is stopped to improve efficiency. EPA-estimated fuel economy is an excellent 22 mpg city/34 mpg highway and 27 mpg combined with the manual and 24/33/27 with the automatic.