What does 'res' mean on a BMW?

[JourneyLynn]

On a car, 'res' stands for the resume function of the cruise control system to restore the set speed. Introduction to cruise control function: When the cruise control button is pressed, the car can maintain that speed. The function immediately disappears when the brake pedal is depressed. How cruise control works: The cruise control component reads the pulse signal from the speed sensor and compares it with the set speed, then issues commands to the servo mechanism to adjust the throttle opening to increase or decrease, ensuring the vehicle maintains the set speed. Range of adaptive cruise control: Adaptive cruise control is not only suitable for highway conditions but also for urban driving conditions, including stop-and-go traffic. In contrast, regular cruise control is only suitable for good road conditions, such as highways with light traffic.

[SanMila]

I've always been fascinated by the features of BMW cars, and the RES button typically refers to the Residual Heat System. After driving in cold weather and stopping while the engine is still warm, pressing RES allows you to utilize the remaining heat to warm up the cabin, avoiding waste and saving some fuel. For instance, when waiting in the car during winter without keeping the engine running, it keeps you warm and is quite eco-friendly. However, it only works right after the engine is turned off—once the engine cools down, it becomes ineffective. I've seen discussions on forums explaining that BMW designed this to reduce cold-start consumption, making it part of their energy-saving technology, especially convenient for long-distance driving. Just ensure your battery is in good condition when using it, or the function might not activate properly.

[DeAnastasia]

As a seasoned BMW driver with over a decade of experience, the RES function stands for Residual Heat, which is quite handy. When you park the car and the engine's residual heat hasn't dissipated yet, pressing the RES button continues to supply warm air, avoiding the need to restart the engine and waste fuel. I find it helps maintain the cabin temperature longer, especially in sub-zero weather, saving both time and fuel costs. Timing is key—pressing it before the car is fully warmed up won't have much effect, but once the engine is hot, it makes a noticeable difference. This feature is thoughtfully designed, showcasing BMW engineers' attention to everyday practicality. Similar cars can also benefit from this during winter maintenance periods.