Since the late 1990’s some automobile manufacturers like Ford, Audi and Mercedes Benz have been using xenon high intensity discharge headlights as an option for consumers when buying a new vehicle and the most common OEM HID bulb had been the D1 series bulb. First there was D1R (for reflector housings) then there was D1S (for shielded housings AKA projectors). The “R” type bulbs have a painted section designed to block light output to a certain part of the housing thus helping to create a safe output pattern. The “S” type bulbs have nothing on the bulb itself because the shield is inside the projector housing.
Then along came the D2 series bulbs, and again we started to see the D2R and then the D2S, with R and S meaning the same thing as the D1 series bulbs.
Now that you have a clear understanding of the difference between the D2 style OEM xenon bulbs and the D1 style OEM bulbs, now I can show you the newest evolution in OEM high intensity discharge lighting – Introducing The Green Movement!
Enter D3 and D4 OE bulbs, D1 and D3 are in the same family, so are D2 and D4. D1 and D3 have an igniter built into the base, whereas D2 and D4 rely on the igniter inside of it’s accompanied ballast. The biggest difference between the D1/D2 VS D3/D4 bulbs is that these new D3 and D4 bulbs use no mercury and require less energy to turn on! The easiest way to tell the difference between a new No-Mercury bulb and the old style is to look at the part that the wire harness connects to and you will see it is green (see top picture).
Many vehicles today are using this type of D3 bulb, including the new Ford Mustang, Ford Flex and all new Audi vehicles like the A3, A4, Q5 and S5. When you are shopping for OEM style D1S, D1R, D1C, D2S, D2R, D2C, D3S, D3R or D3C HID bulbs, you also should know the difference between the S, R and C identifiers. Manufacturers want to make it hard to put the wrong bulb inside your factory HID headlight housing, so they built the bulbs with little notches allowing them to only fit the correct housing type, but otherwise they are identical.
As you can see, the D2C / D1C / D3C / D4C bulbs are all designed to replace either the S or R type bulbs because they have all of the notches for any application. This is great because it allows the cost of the bulb to be less than an OEM product due to needing to inventory only one bulb per style instead of 2 or 3. Before I let you go into the world to buy HID bulbs for your xenon equipped whip, let me make a few things clear:
The “C” type based-bulbs are a great option for replacing any OEM style bulb.
You CANNOT replace a D3 bulb with a D1 bulb! They will physically fit, but the bulb, ballast or both will be damaged when you turn it on.
You CANNOT replace a D4 bulb with a D2 bulb! They will physically fit, but the bulb, ballast or both will be damaged when you turn it on.
D1 and D2 xenon bulbs use Mercury. D3 and D4 xenon bulbs are Mercury-free!
Philips and other OEM producers of xenon lighting in cars DOES NOT offer anything besides 4,300K bulbs. All bulbs listed as Philips or Sylvania in other colors are fakes!