The L gear sends less fuel into the engine, giving it more torque at the cost of power. Although this slows your car down, there are certain situations you may want to use it.
The extra torque from using “L” can be helpful when traveling through mountains or climbing and descending steep hills. It can also be used when driving through dangerous weather.
However, it’s most commonly used for towing. “Low” gives your car more pulling power, making it helpful when hauling a trailer, boat, or another vehicle.