LED tails vs Standard tails for gas mileage?
 

I see many cars with LED tailights, and most of them have about 15-20 led's on each brake light to replace 1 or 2 standard bulbs on each side. does the energy used in the LED's exceed the standard lightbulbs?

for example: a 05 honda accord has 1 bulb for the brake light (2 total) on each side, while a 06 accord has 16 LED's on 1 side (32 total). does this actually save any energy or is it just for looks.

It may save some energy. LEDs can produce the same light with less energy usage. However, they are probably tacked on to a wasteful system that ends up using more energy. That's how OEM automotive engineering often works, in my experience.

OEM LEDs are there for perceived value, looks, and maintenance (since LEDs have a longer service life than incandescent).

The balance of cost vs. re-lamping & the gains may be questionable. It will relieve the system of a few of amps and also extend longer alt. life. This played a big part in savings on trucks I work on with 30 or so lamps on the rear alone that are on the brakes 1000 times & flashers allday long in a day picking up garbage. To re-lamp all is very expensive and although LED's are warranted very well they have issues the same conventional bulbs. In a car reliability is better i would imagine.

there is also a safety advantage. redundency is often used for safety and in this case, there is more than you can shake a stick at.

this way, if one bulb goes out, you still have light on that side.

a side note though. I looked into aftermarket LEDs and noticed that when replacing bulbs with LED boards, on some of the lights (like the turn signals) you are required to use load resistors so the cars computer knows there is a light there and it is not burnt out. it needs to see a certain amount of current draw to recognize that there is a bulb present. obviously not a problem on OEM stuff.

An 1157 bulb draws .6 amp (taillight filament) and 2.1 amp (brake light filament). 12v x .6 amp = 7.2 watts. Other incandescent tail lamps are probably similar. In other words, about 1/100th horsepower per bulb (1 hp = 746 watts). I doubt you'll ever be able to measure a FE difference. And, many LED taillights are strobed, which makes many of them (especially the older OEM types) very distracting...at least to me.

OTOH, LEDs should last a lot longer, and come on instantly, which may possibly reduce rear-end collisions...and that's always a good thing.

Doubt you'll ever recoup the cost you spend on purchasing replacement tails with the reduced energy/$ it costs you to run them.

Here's what I'm thinking about all of this; I am going to put on an underdrive crank pulley, so all of my belt driven things will turn slower. LEDs won't tax the slower moving alternator as much. I'm replacing every bulb that I can with LEDs, and have replaced the 9004 headlights with HID projectors.

simple test: get a voltmeter gauge installed in the car. if, with the underdrive setup, the system voltage is over 13v at the lowest warm idle but when you turn all the lights on drops below 13v, then worry about current draw. till then you aren't 'overtaxing' your electrical system

I like my LED tail and running lights because I like to EOC at night and it doesn't drain my compact 15 pound battery as much.

Thanks! I wouldn't have thought of that.