Originally Posted By: dparm
The only real leg-up anyone has is with stuff like the NightBreaker which has a more efficient and smaller filament, meaning you get more focused (and less wasted) light.
In my experience, Consumer Reports is right that most upgrade bulbs don't offer a significant improvement. There will be some (especially if your car has the original long life bulbs still in it). But it's not dramatic.
Most of the better upgrade bulbs have a completely clear glass envelope. This is good (no light-stealing filters), but it also indicates that the bulb still produces legal levels of light. The bulbs that offer the most improvement are those like the Philips Xtreme Power/Xtreme Vision and Osram Nightbreaker. Look closely: they have a thin blue filter ring at the very front of the bulb. Contrary to popular belief, this blue ring isn't there to color the light for ricers.
It's there to steal away some of the bulb's output to keep the bulb in the allowable range of output. But it does so at the very FRONT of the bulb, where the light is largely unused anyway (being taken up by the glare shield found in front of most bulbs in modern housings). The light output from bulbs is measured in an Integrating Sphere (
Wikipedia link). An integrating sphere measures total output of the light source without respect to spatial direction. In other words, it doesn't matter how the light is distributed inside the sphere...it simply measures total flux. Without the thin blue ring on the front of bulbs such as the Philips Xtreme range and the Osram Nightbreaker, these bulbs would produce extra-legal levels of light.
I say all that to note that although these two bulbs (and perhaps some others) are street legal bulbs, they do produce more of a performance improvement than otherwise possible because of this thin blue ring, which again removes light from areas which aren't used by the housing anyway. These bulbs stand out from the crowded arena of clear-glass upgrade bulbs (and are certainly superior to bulbs with full color filters like the Sylvania Silverstar, GE Nighthawk Sport, etc).
Consumer Reports did not test either the Philips Xtreme Vision or the Osram Nightbreaker. If they had, I believe they would have found more of a performance improvement.
All of this performance improvement, obviously, is at the expense of life. There is no free lunch.