Xenon Bulb Install

Overview:
I had seen a few xenon headlight bulbs advertised and wondered whether they were worth upgrading to. Here are my findings and experiements.

Xtreme White :
I bought a set of Xteme White Xenon bulbs rated at 3900 Kelvin for my VW Golf. Installation was quite difficult as there is not easy access to the headlight compartment under the bonet. Although the bulbs produced a whiter light I did not find the light intensity had been increased. The light colour output was however comparable to the HID Xenon lights found on top-end cars such as Mercedes, just not as bright. According to this article the Mercedes HID Xenon lights have a kelvin colour temperature value of about 4300 K.

Please note that HID Xenon lights are completely different (and much more expensive!) to the standard Xenon bulbs I am referring to here. For information on how High Intensity Discharge lights works see here.

About a year later one of the dipped beam Xteme White Xenon bulbs blew and I needed to find a replacement. I tried the Halford Super Brilliance 50% extra bulbs as they were on special offer. Although they produced a more intense light the colour was the standard more yellow halogen type, as you can see below.

Xtreme White	Halfords Super Brilliance 50%

After some research on the net I found the Osram Silverstar bulbs were very well recommended. Auto Express did extensive testing on a number of bulbs and found the Osram Silverstars to be the best. I also found on their website they are quoted at about 4000 kelvin, so should emit the whiter light I am used to. Update: I have now installed the Osram Silverstar bulbs and they are excellent. However they do appear ever so slighlty "less white" (lower colour temperature) than the Xtreme bulbs even though the Osram Silverstar bulbs claim to be 4000 kelvin and the Xtreme bulbs claim to be 3900 kelvin.

From reading a number of articles my understanding is that to create a more intense light, manufacturers use xenon gas together with high-luminance filament coil that is designed for use at a slightly lower than normal voltage and therefore burn brighter. This "overdriving" decreases the life of the bulb. The whiter light is created by using a filter in the bulb, which actually decreases the intensity of the light but because of the high-luminance filament the overall intensity can still be higher than standard halogen bulbs. Some bulbs do not have the filters and produce more intense but more a more standard yellow light, the Halfords Super Brilliance 50% are an example of these.

It is possilbe to get higher rated (100watts rather than 55w) bulbs for offroad use however they may require relays if the current wiring of the car is not designed for the higher rating. I have seen reports of switches melting when using the standard wiring because of this!

Links:
AutoBulbs Direct - Osram Silverstar and Xtreme White bulbs can be found here.