Scania has introduced an hydraulic retarder—a form of auxiliary brake for trucks—that automatically disengages and enters a freewheeling mode when not active.

This reduces drag losses because both vaned wheels that provide braking power when rotating in oil are disengaged.

Actual fuel savings will vary depending on road conditions, but an average of a 0.5% reduction is taken as the rule of thumb.

When braking power is needed, the free­wheeling stops and the engagement takes place smoothly and immediately using a type of synchronization that is similar to that in Scania gearboxes.

Besides not requiring any energy, the freewheeling retarder also provides higher braking power—4,100 N·m instead of 3,500 N·m—as well as an increased braking effect at lower engine rpm with the help of higher gear ratios.

Reducing fuel consumption is Scania’s main priority. The freewheeling retarder produces further savings that also contributes to an elevated driving experience. The activation of the retarder itself is either initiated by the driver—via a lever on the steering column or with a light touch of the brake pedal—or when the cruise control requests braking. As soon as the retarder is not in use, it freewheels again on its own. But it remains ready to smoothly and firmly change from free­wheeling to full braking power in no time.

Deliveries of the new retarder to customers will begin in the first quarter of 2015.