As I drove around the Florida Keys today I just left my lights on all the time. Those of you who have driven US1 into the Keys know it is dangerous and most drivers turn their lights on during the 20 mile stretch from the mainland to Key Largo. Question. Is there any problem with me just leaving the light swtich on all the time? The lights go off when the key is turned off so I reckon it should not hurt but I figured I ought to ask. Any idea how much leaving the lights on all the time will hurt my gas milage?

LEAVE 'EM ON!

All new cars in Canada have had this feature for years now - and my '88 Volvo was way ahead of its time with the light switch bypass.

The safety factor greatly outweighs any of the other considerations.

Join the 21st century! Drive with your lights on!

I always do.
No problems have creaped up in the past 13 years from doing it.
--
'75 Jeep CJ5 345Hp ChevyPwr and two motorcycles: it wasn't Volvos safety , it was Longevity that sold me

Are you sure the relay extinguishes park lights, tail lights, etc. when ignition is switched off?

Problems with leaving lights on all the time:
http://www.lightsout.org/

Leave your lights on, if you ask me.

I have been driving with no daytime driving lights for many years. There has been many times that a driver in a hurry (that's about 98% of the drivers) would, say, start pulling out of a street of driveway and stop at the last second because they didn't see me at first glance. Since I have been driving a 945 with lights that don't turn off for the past two years I have noticed a big difference in being "able to be seen". It only took a month to notice this difference.

Since then I have persuaded family members to turn on their lights while driving and it has become as routine as putting on their seat belts.

The DRL watt-hours could be added up with a little watts loss added from the alternator, easily and converted to BTUs per gallon or something like that. I'll ask my "genius" son, Volvo Boy, to calculate this unless someone beats him to it. I'm not going to look for my old thermal dynamics book. Good question. My guess is that you would loose 1/4 to mile per gallon at the most. I wouldn't care if it was a two MPG loss.

If I said, leave your lights on earlier, I'll say it again, leave you lights on, of course, IMHO.

--
Tom F '95 945na, lien holder on a '95 944Ti, RIP '78 244

I've got it!

Convert to an electic cooling fan, and leave your lights on. The elec fan almost certainly saves more energy than the lights could use....

I'm not going to do much thinking abou it, but hear this:

two 65 watt bulbs = 130 watts...Lets be really "conservative" and estimate 50% efficiency for the alternator...260 watts...0.26 kW

How many kW per HP? I think we are talking 1/2 HP max....

Insignificant, I say. I'll put my money on the 1/4 mpg guess...

-Steve

0.747 kw per hp.

I think the aero drag penalty of driving with the windows down is more fuel-costly than leaving the headlights on.

I prefer to drive with the lights on all the time, but now that I'm in AZ I've changed to preserve the battery and charging system. With the AC and blower on nearly all the time, plus a relatively short commute these days, the battery barely comes back up to full charge before I park the car. Drawing another 10 amps for the lights makes that voltmeter needle lean a little too far to the left for my comfort.

Effect on fuel mileage? Maybe increase of about 2 deciliters per 100 km. I believe that's ~3/4 cup on ~60 miles US measurements.

In Finland, headlights are required 24/7 through the year. Which isn't such a bad idea, thanks to the low-angle sunlight especially silver coloured vehicles are VERY difficult to see.


-M.R.

We drive all of ours all the time with the lights on. I love the fact that I never have to remember, and I can't leave the lights on by accident. The only time I turn them off is on purpose when I want to park waiting for someone, with the lights off.
I have gone through a couple of bulbs in 6 different cars since 1998... nothing excessive I would say. I don't get more burnt out bulbs in these than in any other kind of cars.
The relays and fuses and so on are all designed for constant use.
--
Rob Bareiss, New London CT ::: '87 244DL/M47- 221K, 88 744GLE- 202K, 91 244 181K, 88 244GL 145K

My daughter has left her light switch on for the last three years. No problems. Great safety. Her's is an 86.
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Thanks to everyone for the help, Doug C. 81 242 Brick Off Blocks, stock, M46; 86 240, 135k

I've ben doing it for over a year now...It hasn't been an issue at all for me...

Two notes, though...

If your alternator happened to go out, you'd want to turn them off to minimize drain on the battery so you can drive further before the battery dies...

Be especially aware of the light switch when you drive a different car...many don't turn the lights off for you, and you can easily forget...

Make sure they are in full "on" mode -- the parking lights will stay on if the switch is in the middle position...

-Steve