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[Selcouth_Feline]

My Volvo has day-running lights (i.e. they are always on - it's a new EU law, although Volvo have had this option for ages). Someone told me that I should consider turning them off because they would help my fuel consumption. Really?? I guess it's because there is more load on the alternator? Does it really make that much of a difference to MPG?

[What's Burning?]

I think that's bullsh!t the alternator runs regardless. Perhaps if you were driving a hybrid and you turned off all the unessesary electronics.

Even if there were to be a difference it would be imperceptibly small. The alternator is running in the car all of the time, it just doesn't turn on for the running lights, and it generates more electrical power than it needs.

EDIT: I forgot to mention... what you will waste more of is light bulbs. I had a V40 wagon that I changed the headlight H7 bulbs on about twice a year!

[FRAFPDD]

Is it really a new law, i havent seen many people with them on.......infact only one, my grandad.

[Selcouth_Feline]

I think that's bullsh!t the alternator runs regardless.

That's what I thought. But then I figured if it *was* the truth, maybe it was because the altenator would use more fuel if more load was being put on it.

Is it really a new law, i havent seen many people with them on.......infact only one, my grandad.

Yup - all new cars must have DRL fitted as standard as of Feb 2011. They don't have to be retrofitted to old cars though.

[darwin dali]

Yeah, Sweden had this law for ages (moose, far north light conditions). We have them cars here as well, but I don't think it's the law (especially across all 50 states). Having this feature usually gives you a break with the car insurance premiums though.
Seriously doubt you'd notice it in the fuel consumption. Driving with the window rolled down for an hour or so will cost you way more. Or having a roof rack. Or schlepping extra kilos of gear you never use in your trunk.

[Jabberwocky]

In theory it would decrease your fuel economy however (remember you can not create or distroy energy, it just changes form) however the amount of energy to light a 5w Bulb is nothing to dragging a 2 ton car around the place.

[bud]

EDIT: I forgot to mention... what you will waste more of is light bulbs. I had a V40 wagon that I changed the headlight H7 bulbs on about twice a year!

day running lamps are LED arent they? On most new cars anyway. I didnt think they needed to be changed?

[myownalias]

EDIT: I forgot to mention... what you will waste more of is light bulbs. I had a V40 wagon that I changed the headlight H7 bulbs on about twice a year!

day running lamps are LED arent they? On most new cars anyway. I didnt think they needed to be changed?

My 2006 car has DRL by default although I can turn them off in favour of the sidelights, no LEDs on most cars in the US; maybe different in Europe!

As for fuel economy; I can't say as all my cars have/had DRL but I wouldn't imagine it would make a difference to fuel economy as the little power it needs comes off the alternator!

[What's Burning?]

We have Audi to thank for LED based daytime running lights. You can't swing a dead cat without hitting a car bought over the last year costing $40k that doesn't have them.


The Volvo V40 I had that had it by default was a 2000 so way before the use of LEDs so the idea has been in use for a long time. You had to go through a sequence to actively disable it. But as stated it's actually useful and you really notice it in the periods of time when you wouldn't normally use your light, dawn, dusk or in an impending storm.

Even better than the DRL though is the high intensity rear fog light, I love it, and only Volvos and German cars (don't know about VW) come into the US with it as standard equipment.

[bud]

Well my car has fog lamps, many people used them as day time running lights here in my state, until the powers at be thought hey theres something we can fine people over and make some revenue. So they banned them unless used in fog conditions. During the day i have no idea why as you are not going to get glare from them Now car makes are ditching them for the LED.

Speaking of glare Halogen head lamps seem way to bright if you ask me. For a person with blue eyes like myself glare at night is a problem

[Jabberwocky]

This interested me so had a look into it

a 100bhp car produces 73kW or 73,000W of energy.

so to had DLR on which say are 5W per corner, 20W total.

so that would be:-

(20/73000)*100 = 0.0273% of you engines power.

If you are averaging 40mpg, with the lights on, you would get
40.01mpg with the lights off

[darwin dali]

This interested me so had a look into it

a 100bhp car produces 73kW or 73,000W of energy.

so to had DLR on which say are 5W per corner, 20W total.

so that would be:-

(20/73000)*100 = 0.0273% of you engines power.

If you are averaging 40mpg, with the lights on, you would get
40.01mpg with the lights off

[Selcouth_Feline]

Seriously doubt you'd notice it in the fuel consumption.

I'm not really bothered about fuel consumption - otherwise I wouldn't be driving some hidesouly large barge. I was more curious as to the theory behind it

Cheers Jabberwocky

[stonemonkey]

Ah, so it's law to have those distracting lights on the tractors at the rear window level of normal cars.

And what's with the blinding brake lights on Audis? sit behind one too long at traffic lights and the shape's burnt into your retina.

Anyway, even though the alternator is always connected it will increase the load on the engine the more current is taken from it. The low power lights/bulbs/LEDs used now probably won't take much though.

[What's Burning?]

Speaking of glare Halogen head lamps seem way to bright if you ask me. For a person with blue eyes like myself glare at night is a problem

I think the bright blue/white hue of xenon headlights looks badass. Sorry about your baby blues.