Quote:
Originally Posted by 101mpg
I'd also suggest buying the brightest lights for every exterior part of your vehicle you can find. Super-bright taillights help a LOT, side marker superbrights, the brightest headlights you can afford, etc.
Personally I drive with lights on at ALL TIMES.
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Lights are a good idea, but they are clearly a trade-off.
Yes, they make you more visible, but (due to their electrical power load) they are bad for FE. So you want to use them when you "need" them, but not overuse them (and therefore get lower FE than you otherwise would).
This is true, because in almost all cars (cars with grid charged battery packs are one notable exception) every watt of power you use comes from the alternator (although that electricity may be temporarily stored in the battery before you use it, it still comes from the car's alternator). And where does the alternator get its power from? You guessed it, virtually all alternator power comes from additional mechanical load (and therefore additional fuel use) against the gas engine. So far from being "free" in a car, electricity is actually amazingly expensive (in terms of cost per kilowatt used) in a car. And the more gas prices rise, the more costly that (car generated) electricity is becoming all the time!
As a result, many of us have gotten significant FE gains, simply by saving electrical power in a car. And one of the significant uses of electrical power (fans are another big electrical power drain) is the many car lights burning up a lot of watts of (electrical) power.
OTOH lights are often needed for both safety and legality, so you can't get away from them entirely (despite the FE benefit, if you could). And you are also correct that sometimes when they aren't technically "needed" (from a legal standpoint), some lighting can be very useful in making your car easier to be seen. So we clearly have a trade-off here (saving electricity, and therefore better fuel economy, vs the safety and legal reasons for using lights).
One thing I've found that can make a big difference, is converting your car lights to (very bright, not the cheap bad) LED modules. You can't do this with your headlights, but you can do this with virtually every other light in the car, and the power savings can be very significant. I've done this, and I was able to save several amps of power (when my lights are on). Not perfect, but much better than the electrical load before.
So what do I do? I generally only run my headlights when I think they are really "needed" (often for legal reasons, such as driving at night), because even the low beams use a lot of watts (about 110watts just for the two lights + whatever power the secondary LED lights use). However, I do run my (converted to LEDs) secondary lights (everything EXCEPT the headlights themselves), whenever I feel that turning them on would make my car significantly easier to see. Because in that case the safety concerns override the power cost (only a few watts of power for the entire set of car LED modules, due to the fact that the LEDs are SIGNIFICANTLY more power efficient than the conventional lights the LED modules replaced). However, on really bright days (when I don't think the lights will add much to my car's visibility), I just turn off all my car lights, and go with the lowest possible electrical load (and therefore the potential of even high FE than even my secondary lights give me).
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