Do headlights hurt mileage?
Thread Starter
Race Director
Joined: Dec 2002
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From: SCMR Rat Pack'r Charter Member..Great Bend KS
Do headlights hurt mileage?
Just got home from a 1500mile "run" in the Assassin.
Early this morning, on a long, flat straight in Utah, I put the cruise control on 80, (with the lights on) and noted the instant mileage readout. I then turned the lights off, expecting the improved aerodynamics to come into play and see a slight increase in mpg. To my surprise and horror, the instant mpg DROPPED from 31 to 27! I turned the lights back on and the readout instantly went back to 31....even before the lights flipped up. Back and forth I went...each time turning the switch on or off affected the mileage readout.
Anyone else had this happen??
Larry
code5coupe
:seeya
Early this morning, on a long, flat straight in Utah, I put the cruise control on 80, (with the lights on) and noted the instant mileage readout. I then turned the lights off, expecting the improved aerodynamics to come into play and see a slight increase in mpg. To my surprise and horror, the instant mpg DROPPED from 31 to 27! I turned the lights back on and the readout instantly went back to 31....even before the lights flipped up. Back and forth I went...each time turning the switch on or off affected the mileage readout.
Anyone else had this happen??
Larry
code5coupe
:seeya
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From: Exit 89 GSP,Lakewood,NJ The Land Of Mojo
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Re: Do headlights hurt mileage? (rocco16)
That's wierd, we tested my friends Celica, with teh headlights down he could go 5 mph faster.
Safety Car
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From: SCMR Rat Pack'r Charter Member, Inland Empire Chapter
Re: Do headlights hurt mileage? (rocco16)
Maybe its breaking up that bad low pressure zone at the base of the windshield Ive heard about. Odd about the mileage as mines always almost 40 mpg till I hit about 90-95 mph. :D
Le Mans Master
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Re: Do headlights hurt mileage? (vinnies87)
It shouldn't make a noticable difference one way or the other. Maybe the added load of the headlights is dropping the system voltage enough to affect the computer. Have you tried running with the headlights up, but not on?
:cheers:
:cheers:
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From: SE NY
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Re: Do headlights hurt mileage? (rocco16)
I only notice a slight drop in mileage with the top off, but headlights up/down don't seem to effect the readings.
I too suggest you try the test with headlights up/down but off, as you may have a voltage or grounding "gremlin" aboard.
I too suggest you try the test with headlights up/down but off, as you may have a voltage or grounding "gremlin" aboard.
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From: Hinckley Ohio
Re: Do headlights hurt mileage? (rocco16)
Well from a theoretical view turning headlights on takes power. The only place this power can come from is the motor & the gasoline that powers it, so from that point of view you should expect lower mileage with headlights on.
The aerodynamics of the raised headlight would intuitively increase "drag" and thus reduce mileage.
On the other hand, both these effects would be "small" so a difference would be hard to isolate. For example two 55 watt headlights total 110 watts. I think 1 hp is 776 watts or there abouts, so it really doesn't make much difference.
Personally the first time I ever heard about headlights effecting car's performance was in about 1959 when I, as a teenager was on day trip with a friend and his Dad, a mechanical engineer, who said that we would get less gas mileage on the way home from this trip since it would be dark & lights would be on.
The aerodynamics of the raised headlight would intuitively increase "drag" and thus reduce mileage.
On the other hand, both these effects would be "small" so a difference would be hard to isolate. For example two 55 watt headlights total 110 watts. I think 1 hp is 776 watts or there abouts, so it really doesn't make much difference.
Personally the first time I ever heard about headlights effecting car's performance was in about 1959 when I, as a teenager was on day trip with a friend and his Dad, a mechanical engineer, who said that we would get less gas mileage on the way home from this trip since it would be dark & lights would be on.
Melting Slicks
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From: Construction Sucks! MI
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Re: Do headlights hurt mileage? (Mr Mojo)
That's wierd, we tested my friends Celica, with teh headlights down he could go 5 mph faster.
Melting Slicks
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From: Minnesota in the summer, Las Vegas in the winter
Re: Do headlights hurt mileage? (rocco16)
Perhaps what you thought was the headlight switch was actually known technically as RPO AAD:
Automatic Anchor Drop.................. :rofl:
Automatic Anchor Drop.................. :rofl:
Thread Starter
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From: SCMR Rat Pack'r Charter Member..Great Bend KS
Re: Do headlights hurt mileage? (65Z01)
I'll try the headlights up/off next time out.
I expected a betterment in mpg with the lights off, not the opposite. My gut tells me there is an electrical gremlin loose, since no one else reports a similar occurance. No other electrical anomalies though.....
Sidebar: In 1500 miles of driving over two days, I saw exactly TWO Corvettes on the road (one C5, one C4)...no Mustang Cobras, no Vipers, one 911 with which we "flew in formation" for an hour or so. Minivans by the hordes, Camry's by the dozen, and a surprizing number of Olds Aurora's. Where are all the performance cars?????
Larry
code5coupe...the Assassin
:seeya
I expected a betterment in mpg with the lights off, not the opposite. My gut tells me there is an electrical gremlin loose, since no one else reports a similar occurance. No other electrical anomalies though.....
Sidebar: In 1500 miles of driving over two days, I saw exactly TWO Corvettes on the road (one C5, one C4)...no Mustang Cobras, no Vipers, one 911 with which we "flew in formation" for an hour or so. Minivans by the hordes, Camry's by the dozen, and a surprizing number of Olds Aurora's. Where are all the performance cars?????
Larry
code5coupe...the Assassin
:seeya
Drifting
Joined: May 2002
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From: "Drive like Hell, you'll get there faster." Tucson AZ
Re: Do headlights hurt mileage? (rocco16)
Actually they do.....but it's so small you shouldn't even notice until you're doin about 90-100 mph. The ECM's just trying to compensate for it. Notice when you fill up a tank how it will never really show it as full all the time. The ECM tries to compensate for so much that I have no choice but to question it's accuracy. It's accurate ENOUGH , but not 100 percent. The headlights thing is really just an aerodynamical physics issue, but I think the ECM is getting it's data from the weight distribution. Stock headlight lamps are glass I believe. If it's that much of a Big deal to you, try replacing them with some plastic lamps/lenses if you don't have em in already. It's alot less weight and therefore alot less weight that gets distributed to the front end when the lights flip. Keep in mind though I think it's like 60 percent lighter, but 60 percent of a pound or two is what you're dealing with at most if they weigh even that. Like I said though, performance wise it shouldn't make a difference unless you're constantly at high speeds. :steering:
Drifting
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From: "Drive like Hell, you'll get there faster." Tucson AZ
Re: Do headlights hurt mileage? (Mr Mojo)
That's wierd, we tested my friends Celica, with teh headlights down he could go 5 mph faster.
Pro
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Re: Do headlights hurt mileage? (rocco16)
Headlight weight, volts=hp, and headlight aerodynamics DO NOT significantly affect mileage like in this manner. You have an electrical problem which is the cause of the false reading.
*Something to think about: opening and closing the headlights at high speeds (or at any speed except for at a dead stop) HIGHLY effects the wear/life of the headlight rotation points. Never open or close your headlights unless you're at a dead stop. Bumps/jarring and wind resistance/pressure on the mechanism as it is rotating causes great wear.
Good luck, bro!
*Something to think about: opening and closing the headlights at high speeds (or at any speed except for at a dead stop) HIGHLY effects the wear/life of the headlight rotation points. Never open or close your headlights unless you're at a dead stop. Bumps/jarring and wind resistance/pressure on the mechanism as it is rotating causes great wear.
Good luck, bro!
Burning Brakes
Joined: Aug 2003
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From: Ft. Walton Bch. Florida
Re: Do headlights hurt mileage? (Silver 96)
It shouldn't make a noticable difference one way or the other. Maybe the added load of the headlights is dropping the system voltage enough to affect the computer. Have you tried running with the headlights up, but not on?
:cheers:
:cheers:
Burning Brakes
Joined: Feb 2002
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From: Pittsburgh PA
Re: Do headlights hurt mileage? (C-4 Cross Fire)
*Something to think about: opening and closing the headlights at high speeds (or at any speed except for at a dead stop) HIGHLY effects the wear/life of the headlight rotation points. Never open or close your headlights unless you're at a dead stop. Bumps/jarring and wind resistance/pressure on the mechanism as it is rotating causes great wear.
Good luck, bro!
Good luck, bro!
