Dear Tom and Ray:
I enjoy your column every week. In our cars, the headlights turn off automatically when we exit the vehicle, so there's no danger of leaving the lights on and draining the battery.
So my wife and I just leave the headlights on all the time when we're driving. I think if anything, this is safer, as does she. Is there any reason not to drive with the headlights on all the time? What about the fog lights? Unless you have a reason not to, we'll continue to do it. Thanks.— Rob
Tom: The only real downside is that you'll have to replace your headlight bulbs more often.
Ray: But if you're willing to pay that price for the additional visibility you get, you're certainly not doing any damage to the car.
Tom: It does take a little bit of energy to power the headlights, and that energy ultimately comes from the gasoline. So your mileage will be reduced by a very small degree. It might not even be measurable to you, but it will make a small difference.
Ray: All of this applies to the fog lights and driving lights, too. I would caution against leaving auxiliary driving lights on, because they're often the equivalent of your bright lights. That'll just annoy oncoming drivers, and they'll crash into you on purpose, negating the enhanced safety you get from the lights.
Tom: But we agree with you — driving with your lights on is safer. The easier you are to see, the more likely that other drivers will see you. And if you're willing to pay the price in bulbs and gas mileage, light it up, baby.
Dear Tom and Ray:
I may be dreaming, hallucinating or even suffering from dementia. I seem to remember something from my childhood that other people my age do not.
When I was but a tadpole, I seem to remember my dad checking the water level in the car battery. The top of the battery was covered with a thick, tarlike substance, into which he would push copper pennies next to each battery terminal.
The reasoning behind this was to draw the potential corrosion away from the terminal and toward the penny. Did I dream this, or did people used to do this? Please tell me if I'm demented or not.— Art
Ray: We don't have enough information to answer your last question, Art. And the fact that you're writing to us for advice definitely is a strike against you. But you're not dreaming about the pennies and the batteries.
Tom: It's based on the theory of sacrificial anodes, in which you "sacrifice" a more reactive metal — copper, in the case of pre-1983 pennies — to protect a second, less reactive metal — the lead battery terminal and connector.
Ray: And in the old days, when batteries were covered with tar on top, you could warm up a penny with a match or a cigarette lighter, and then slide it into the tar half an inch away from the battery terminal. The penny always would corrode first.
Tom: Nowadays, most batteries are sealed in plastic, so the acid — which is what causes the corrosion — rarely escapes the inside of the battery. That makes a sacrificial anode far less necessary. And besides, these days, we all have to save our pennies.