The XTAJ category at Sixt might sound a little mysterious at first, but it’s actually your ticket to a rental experience that’s anything but ordinary. If you book in this class, expect a convertible two-seater built more for fun than practicality.
Sixt XTAJ
Find out which cars are included in the Sixt XTAJ category
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BMW Z4 Roadster
The BMW Z4 continues to be a reliable member of the Sixt rental lineup in the US. This two-seater roadster, with its classic rear-wheel drive and soft top, is available in two trims. Under the internal code XTAJ, you’ll find it as the Z4 sDrive30i with a four-cylinder engine, and as the more powerful Z4 M40i, which features a straight-six. Both come standard with an 8-speed automatic transmission.
The entry point into the Z4 lineup is the sDrive30i. Powered by a 2.0-liter turbocharged four-cylinder engine, it delivers 255 horsepower and 295 lb-ft of torque, launching the roadster from zero to 60 mph in around 5.2 seconds. That’s more than enough for everyday driving and makes for an enjoyable experience on twisty backroads. Torque kicks in early and remains smooth throughout. The engine stays fairly quiet, though it maintains a refined, composed character. The 8-speed automatic shifts smoothly and unobtrusively, picking gears smartly. When paired with the optional adaptive suspension (part of the Dynamic Handling Package), the Z4’s behavior becomes more responsive, with firmer damping and sharper steering feel.
The M40i, on the other hand, is clearly the performance star. With around 382 horsepower from a turbocharged inline-six, it delivers instant punch and a noticeably more aggressive sound. It does the 0 to 60 run in just about 3.9 seconds when equipped with the automatic. For purists, BMW now offers the M40i with a 6-speed manual transmission, which is a rare option these days. That version is aimed at drivers who want to skip the electronic aids and enjoy a more mechanical connection without sacrificing modern tech. However, this manual variant is not available through Sixt.
Despite its sporty nature, the Z4 remains a surprisingly comfortable roadster. The suspension absorbs bumps with ease, even in the M40i with adaptive M suspension. Steering is direct without being twitchy, making it easy to live with in daily driving. Drivers can switch between drive modes that range from relaxed to sporty. The manual M40i variant, in particular, delivers more tangible feedback and connection to the road.
Inside, the Z4 features a clean, modern layout. Materials include leather, aluminum, and high-grade plastics. Depending on the trim, you’ll find aluminum or gloss black accent strips that add a sporty yet refined look without overwhelming the design. Build quality is solid, front-seat space is adequate, and the trunk is reasonably sized for a roadster.
A digital gauge cluster and a 10.25-inch infotainment display running BMW’s iDrive 7.0 system come standard. Both are user-friendly and well-organized. Additional options include a head-up display, Harman Kardon premium audio system, and ventilated seats.
The seats strike a good balance between comfort and lateral support. They’re power-adjustable as standard and allow for an ergonomic seating position, even on longer drives. The upholstery is high-quality Sensatec synthetic leather, with optional Vernasca leather available in a variety of colors.
The base Z4 sDrive30i covers all the basics when it comes to comfort and safety, but BMW keeps some features reserved for optional packages. Standard equipment includes automatic climate control, the digital instrument cluster, the central infotainment screen with iDrive 7.0, and power-adjustable sport seats. However, navigation, automatic high beams, and heated seats are only available through add-on packages.
The available Premium Package adds convenience features like ambient lighting, keyless entry (Comfort Access), and remote engine start. These upgrades improve everyday usability, though by now they’re pretty standard in this segment.
For those looking for more driver assistance tech, the optional Driver Assistance Package includes lane departure warning with steering intervention, active cruise control (though Stop & Go is only partially supported), and parking sensors with a rearview camera. But don’t expect more advanced systems. There’s no blind-spot monitor or full lane-keeping assist available, not even as an optional upgrade. That puts the Z4 behind many mid-size cars when it comes to active safety features.