Which headlight bulb should you choose?

"Bright eyes burning like fire...."

HeadlightsWhich headlight technology is best for your car? 

There is an amazing selection and range of options to choose from.

When confronted with choice we humans usually make silly decisions and go with the cheapest or most expensive option or just altogether give up and leave the shop.

Let's look at the options around there are bulbs that were 40%-80% brighter than normal ones at twice the cost.

Then there were bulbs which had a bluish hue and claimed to run at the same temperature as HID lamps at a similar price to the 40% brighter ones. (Having tried these before I was disappointed that the light emitted did not have a the bluish hue the packaging had subtly implied but not actually stated!)

Remember this simple fact, a blue bulb actually filters out blue light. The glass color acts as a filter. 

I would guess that with a fixed wattage going in the brighter bulb would be more efficient and emit less heat and more light. I was also hoping for the brightest light I could get.

There are also super high wattage bulbs around. Peaking at 125w and with an 80W option of pure light they seemed to offer everything I wanted. Sadly though after reading the packaging I determined that these were only legal for street use on cars registered many years ago.

Why the law restricts the wattage of bulbs when it should really be the light output that is restricted makes no sense to me.

What is the difference between Xenon, halogen and HID?

Almost as soon as the motorcar was invented the headlight appeared. Early ones were in a fixed headlight unit so the whole thing had to be changed. They used Tungsten filaments and this was actually fairly inefficient.

Heat output was high so light output was much lower. The light given off appears to be yellow because it is at the lower end of the light spectrum. The filament also burns out slowly over time so as it gets older it gives off less light.

Then we had a breakthrough in Tungsten Halogen technology. Now over 30 years old this technology has been refined and perfected to give us the range of bulbs we have today.

Early bulbs were made of heat resistant Quartz and then later bulbs were made from heat resistant glass. The gas used is generally Argon although called halogen in this application! These bulbs can burn longer and hotter so are able to give off more light giving it a whiter appearance.

The brighter you go the whiter the light gets. Modern lights now use Xenon/halogen gas mix which enables the filament to last longer.


HID (high intensity discharge) is the new kid on the block. These HID lights usually take a few minutes to reach full light intensity although they obtain 70% brightness within a few seconds so are still suitable for a quick flash of the lights. This uses a highly charged current to create a bright arc across a small gap and is incredibly bright and white.

Sadly most HID upgrade kits are not legal in many areas. 

The beam patterns from a HID kit are different to those produced by a standard bulb so you may have to get your headlight lenses adjusted or altered to create the legally required beam pattern.

In the UK cars need automatically leveling headlights and washer jets to make these legal. These lights give a bluish/purple hue due to the light frequency they emit. HID was not an option open to me so I will discuss HID headlights in another article in more detail.

So what did I go for and was it worth the money?

It is annoying having to keep changing the bulbs for MOTs and having other drivers flash you so I opted for the Philips 80% brighter ones and set about proving to myself that they were worth the 3 times the cost of a standard bulb.

I replaced the bulb, but this time round it only took a few seconds. This was probably due to the fact that I had loosened up the housing and connectors last time plus the knowledge I gained on which orientation the bulb required to clear the battery and other components.

I then did a very thorough scientific test. Leaving the standard bulb in the other light and cleaning both lenses to establish a matched control group I turned on the engine and switched on the lights. Then I got out of the car, walked a hundred paces and turned round to inspect the bulbs.

I really shouldn't be so cynical. The new bulb was clearly brighter than the other one. As I moved from left to right and then moving in closer I continued to check for brightness and my original conclusion was right. The new bulb really was brighter. It is hard to judge 80% brighter by eye so perhaps I will get my cameras light meter out and take some measurements.

It is worth noting that often brighter bulbs and higher wattage bulbs have a much shorter life span.

It's now 3 years later and I'm pleased to report that the new bulbs are still going strong, they are still quite bright and work well.

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