Used 2018 BMW 6 Series Convertible Trims Comparison

Under the hood for the 640i is a turbocharged 3.0-liter engine (315 horsepower, 332 pound-feet of torque). An eight-speed automatic is the only transmission choice. Standard feature highlights include 18-inch wheels wrapped in all-season tires, keyless entry, a rearview camera, parking sensors, heated front seats, automatic high beams, navigation, Bluetooth, wireless phone charging, Wi-Fi hotspot, and a nine-speaker sound system.

The 650i adds a powerful turbocharged 4.4-liter V8 (445 hp, 480 lb-ft of torque). Aside from the engine, this trim gains a few features that are optional on the 640i, such as 19-inch wheels, upgraded power adjustable seats and a 12-speaker Harman Kardon sound system.

BMW offers a variety of premium color, upholstery and trim upgrades, providing buyers plenty of opportunities for personalization. While some stand-alone options are available, most upgrades are grouped in packages. A heated steering wheel only comes in the Cold Weather package, for instance, and you must order the Executive package for ventilated seats. The M Sport package introduces a sport body kit, a sport steering wheel, a higher top-speed limit, and package-specific 19-inch wheels with either all-season or summer tires.

Blind-spot monitoring is not standard but is available in the Driving Assistance package, which also includes a head-up display, lane departure warning, and front collision warning with low-speed automatic braking. An upgraded Driving Assistance Plus package adds adaptive cruise control and enhanced front collision mitigation. When you select the Parking Assistant package you get an automated parking system and side- and top-view cameras.