As time goes on, your bulbs will start to dim and the quality of the light will begin to decrease. If your bulbs are installed at different times, the quality of one bulb decreases at a different rate to the other bulb which leaves an obvious light imbalance.
If your bulbs are from the same manufacturing batch and are installed at the same time, then they are likely to eventually fail close together. If your bulbs are not installed at the same time then they could fail at very different times, which could potentially cause more problems.
If the bulbs are failing at different times you will have to keep replacing just one bulb at a time. This will mean more time and effort being used. We would recommend changing them both at the same time, so that you have to repeat the process less often.
We all know those cars on the road... those ones that have one really bright headlight, and the other is dim. Or, one side of the car produces a white light, while the other has a standard colour. Different products produce different amounts of light and even different colours. Having one bulb dimmer or a different shade to the other could prove distracting for you and other drivers on the road.
If you replace bulbs at different times, you're not going to get a perfect match. Make your car (and other drivers) happy by replacing both headlight bulbs at the same time. You'll benefit from a perfect colour match, as well as evenly-matched beam patterns and brightness.
Don't forget: as an extra step, check the alignment of your headlights when you fit a new pair of bulbs. You can find our step-by-step guide to aligning your headlamps here.
For more information about how to change your bulbs you can take a look at our general step-by-step guide. Alternatively, and for advice specific to your vehicle make and model, we would advise contacting your vehicle manufacturer, local garage, or vehicle handbook.
Here at PowerBulbs, we tend to sell halogen bulbs in twin packs. We believe that the best way to change your bulbs is in pairs. You'll save yourself hassle in the long run, plus you'll get that perfect headlight match.
Shop halogen car bulbs here. Shop xenon HID car bulbs here.