There is a general misconception that a higher K rating provides more light than a lower K rating with Xenon HID lights. The brightest light is actually at a pure white light without any additional colors. With Lumens Xenon HIDs, you would see pure white at 6000K. OE manufacturers choose a light at 4300K rather than 6000K. 4300K has a slight yellowish color (like the color halogen bulbs have). This is not the brightest color band for a clear night; 6000K would provide more visibility in this case. Unfortunately, pure white light does have its downfalls. Because of its intensity, white light (6000K) also refracts back at the driver the most when there are particles in the air (ie. rain, snow, and fog). A less refractive light would be more useful in these conditions; we find yellow (3000K) to be the most effective in these situations. For OE manufacturers, they try to give the medium which would be between the white and the yellow for overall driving conditions.