You know, sometimes it depends on how you look at it.
If you're using the truck's engine for the purpose of taking you
from place to place, then you would say it's 15% efficient.
But if you're using the engine for the purpose of heating the
garage, the pavement, and the air along the highway, then
you would say it's 85% efficient.
Same with an incandescent light bulb. It uses electrical energy
from the wall outlet, and turns maybe 20% of that into light and
the rest into heat. The efficiency of the bulb depends on whether
you're using it to light your closet, or to heat your closet.
I'm just sayin. I've never heard anybody discuss it like this.
