.5 mpg on a 40 mpg vehicle is pretty insignificant....a 1.25% savings.

So, if you save the same 1.25% on a truck that gets 6 mpg, you'll see a whopping 0.075 mpg savings....not even enough to really notice.

Originally Posted by Pedigreed Bulldog

.5 mpg on a 40 mpg vehicle is pretty insignificant....a 1.25% savings.

So, if you save the same 1.25% on a truck that gets 6 mpg, you'll see a whopping 0.075 mpg savings....not even enough to really notice.

$900 is $900 (based on 120K annually) seems worth it to me.

Using lights on a truck is what it is. You're always going to have certain parasitic loss. If it's that big of a deal then install Led's. I doubt fuel mileage will improve but at least your lights will pay for themselves by lasting 10x longer than incandescent.

Originally Posted by JDP

$900 is $900 (based on 120K annually) seems worth it to me.

A 0.075 mpg is such an insignificant "change", there is no way to attribute it to anything specific even if you DID notice it. Were you running lighter? A tail wind? Running more flat ground? Hitting more green lights? Less traffic jams? Too many variables which might contribute to that less than 1/10 of a mpg difference.

Originally Posted by windsmith

I'm just curious about what the actual savings would be. Would it be worth avoiding running at night, turning your lights off during the day, or installing low power LED lighting for daytime visibility in place of the headlights?

By avoiding running at night, you'll be more likely to sit in traffic...and whatever "gains" you are able to make by not running the lights will be eaten up 10 times over by getting caught in traffic. The "savings" are insignificant, so to spend a ton of money trying to chase that tiny little savings you MIGHT see is just a ridiculous waste.

I'm not arguing that you probably wouldn't see any gain, nor could attribute it specifically to turning your light off. I'm just saying that a gain is a gain and 1% here and another there adds up to money in your pocket.

I never ran with my lights on in the day anyways. You're just exposing yourself to the DOT to pull you over if something stupid like a marker light is out.

Parasitic loss is a major issue whether it's due to electrical generation, hydraulic power steering, or freon compression. Freon compression in the AC compressor accounts for up to 50% of fan-on time which when the fan is on at highway speeds decreases fuels economy 8-12%.

http://cumminsengines.com/assets/pdf...whitepaper.pdf