Originally Posted by nfnsquared

That's only true if you use ultra-low-voltage blinker fluid.

Originally Posted by losiglow

I'm not a physicist but we crunched a few number like this in physics class back in my college days. Yes, doing this would put a little less strain on the alternator and thus a little less drag on the engine. But we're talking very little. Just to throw some numbers out -

If you switched all your exterior lights to LED's you'd probably be looking at a 200W max savings between headlights, DRL, fog's, sidemarkers and taillights. That's probably a higher number than reality since the headlights use 70W total (35W x 2) and are by far the largest consumer of electrical power of the bunch.

200 watts / 14.4 volts (when alternator is spinning) = about 14 amps.

(again, not completely true since mechanical drag isn't included, but good enough for our estimates)

Amps x Volts = Watts
Watts / 745.7 (one HP) = Electrical HP Produced by the Alternator
HP x 15% Efficiency Loss = HP Loss
HP + HP Loss = Total HP Used


Our Example:
14 Amps x 14.4 volts = about 200 watts
200 Watts / 745.7 = .27 HP
0.27 HP x 15% = 0.04 HP
0.27 + 0.04 = .31 HP Total (theoretical)
.