Dear Car Talk:
My wife always drives with the headlights on; I do not. I try to tell her the lights only last so long, so use them just when you need them. Plus, with cars these days, you can't just pop out the lens, plug in a new bulb and pop the lens back on. She says that's ancient thinking, and that today's lights last far longer than they used to.
It's been a while since high school auto shop, but help me out here. There is a week's worth of cooking and dishwashing riding on your answer. -- Steve
Well, you're technically correct, Steve. A headlight only has so many hours in it.
But you can say the same thing about a seatbelt. Or the lightbulb you use to get down the stairs at night. And you wouldn't worry about the cost of using those things, would you?
Many studies have found a 5% to 10% reduction in head-on collisions when drivers use their daytime running lights during daylight hours. Presumably, headlights, being brighter, would be at least as effective, if not more.
So it's safer. The issue is, what's the cost? Well, there's a small cost in fuel economy, because there's no free energy. But it's tiny. Less than 1% for DRLs.
What about the bulbs? Typical halogen bulbs last in the neighborhood of 1,000 hours. So if you travel at an average of 40 mph and use your headlights all the time, you'll be replacing your bulbs every 40,000 miles or so.
For how much? About $30 a bulb. So, if you drive 13,000 miles a year, that'll cost you $60 every three years. Or, five cents a day. If you only use your lights at night, you'll spend about half of that, two and a half cents a day.
But if your wife gets into a head-on collision because her lights are off, the co-pay for the emergency room visit will be hundreds, if not thousands of dollars. And your car insurance won't cover the full replacement cost, so add another $5,000 there. And then, for however many weeks or months it takes your poor wife to recuperate, you'll be doing all the cooking and dishwashing.
Even with more expensive HID headlights that some cars have (which cost a lot more but last a lot longer, too), I think the safety argument outweighs the cost.
So take the "L" here, and do your one week of chores now. And be grateful you're able to make your wife safer for a few cents a day.