Does a car burn more gas when its lights are turned on?

Question

Strictly speaking, does a car burn more gasoline when its lights are turned on? And does the overall consumption of gas depend on whether or not the engine is running?

Answer 1

Yes it does, but the difference is so small it should be considered insignificant.

If the car is not running you obviously aren't using any gas, just draining the battery. If the car is running the alternator will cause the car to idle a little higher in order to draw current to run the lights.

Like I said though- insignificant. You're not going to save the world's supply of oil by shutting your lights off while idling in a driveway for a minute.

Answer 2

if the lights are turned on, they need electricity. The electricity is produced by the alternator which is coupled to the car's engine. If you need more electricity the alternator will offer more resistance to the motor, which will require a bit more fuel.

This is true of anything that uses electricity in the car. First and foremost, the air conditioning (which is why, on cars with smaller engines, when you turn the A/C on you can clearly feel that the car seems slower).

As for consumption of gas depending on whether the engine is running - is this a joke or what? Or have I misunderstood? Clearly if the engine is not running, you won't be consuming gas. In such a case you could still use lights, hi-fi, by using electricity stored in the battery. But then next time you start the engine, the alternator will have to recharge the battery, so there will be more gas consumption.

Hope this helps

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Answer 3

Yes, but the the difference isn't something you'll notice when you fill up your tank.
Any electrical draw from the battery requires recharge from the alternator. The alternator will put a slightly greater amount of strain on the engine, which requires more gas. Fortunately, modern bulbs burn brightly with very little electricity. If you want to be extra careful, spend a little more for Xenon light bulbs. My car started after work (9hours) even though I had left the lights (Xenon) on all day.

Second, the overall consumption of gas does depend on whether or not the engine is running. If you want to use your car lights for a few minutes, but you're not going to be driving you will save gas by using your lights with the engine turned OFF. It would take me a full essay to make sure I explain this in detail. An important exception is that starting your car takes far more gas than running your lights for a few minutes, so if your engine is already running and you are going to use it again shortly it is best to leave it running.

Answer 4

Actually yes, the lights ARE run off the battery, but all electricity in the battery is derived from the alternator, which is turned by the engine, so all energy from the battery ultimately comes from the burning of gasoline.

I don't know that the car burns more gas so much as it produces LESS drive, but I think it is the former. You can actually hear the engine rev up more on some cars when the AC is turned on.

That said, in either case the lights are a minute power drain. I think there are 12 lights on the exterior of my car. Assuming they are all ~60 watt bulbs, that is 720 watts. The total output of my engine is probably around 150 hp, which converts to about 110 kilowatts. So the total amount of extra gas being used or milage lost is less then 0.6% of the car's total power.

In other words is not worth worrying about.

Answer 5

The answers you're getting are amazing! Electrical components in the car run off the alternator when the engine is running. When the engine is not running, they use the battery for power. Therefore, when the engine is running, operating your lights or any other electrical accessory will draw power from the alternator, which in turn gets its power from the engine.

The simple answer to your first question is that running your lights will consume electricity from the alternator and make your gas mileage marginally lower.

Yes, the overall consumption of gas depends on whether or not the engine is running. If the engine is off, no gas is consumed at all. Gasoline is only consumed when the engine is running.

Answer 6

I've read all the answers to your question and everyone is right......but there is a slight problem. The electrical system in your car does run off the battery ...until battery load or draw signals the alternator to start adding current. At that point the alternator begins to charge which requires power from the engine to do so. So yes your cars does burn more gas when the lights are turned on. That's why the battery is so important, when it's in poor shape it won't hold a charge as well, and also loses it's buffering capability as it ages. This buffering ability protects fragile electronic components from damage from current spikes etc.

Answer 7

When the car's engine is running, the alternator is being driven by a belt off of the engine. It constantly is creating electricity to charge the battery which is powering the lights. It creates the same amount of electricity whether or not the lights or on or off. So, the fuel consumption is the same. It is not like an AC compressor which has a clutch to engage or disengage from the engine.

"And does the overall consumption of gas depend on whether or not the engine is running?"

If the engine is not running it is not using gas thus at it's most economical. You can figure out the other alternative yourself.

Answer 8

Yes, the car will burn more gasoline with the lights on, but not much more.

It takes energy to drive the alternator which charges the battery. The lights drain the battery so the alternator has to work a little harder to keep it charged.

If the engine is off while the lights are on, no gasoline is used ... until you start the engine again and it has to recharge the energy lost from the battery.

Answer 9

To all of you losers who said "no", why don't you take a few minutes and look it up rather than displaying your ignorance.
Yes, daytime running lights use up gas. The lights are gasoline powered - true, it comes from electricity generated from the alternator but what do you think powers the alternator??? In fact, if all cars in the US were required to have daytime running lights (like they do in Canada), it would cost over half a billion dollars in additional gas consumption.

Answer 10

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