not using radio?

[Geonerd]

Think people!
A good sounding stereo consumes maybe 100W at maximum.
That's about 1/6 of a horsepower.
Average power draw will be much lower, unless you're trying to induce permanent hearing loss.

Enjoy the music and try not to obsess about the 0.05 MPG you are sacraficing!

[DracoFelis]

Originally Posted by Geonerd

A good sounding stereo consumes maybe 100W at maximum.
That's about 1/6 of a horsepower.

Actually the 700 watts is approximately 1 HP rule, is really only true for systems that are 100% efficient. And since car alternators, batteries, etc, are generally not even close to 100% efficient, you are probably looking at something closer to 300 watts (of usable power) in the car causing a 1 HP drag on the engine.

Also, keep in mind that most small (fuel efficient) cars use/need very few HP at highway cruising speed, so even a somewhat "small" HP drag from the alternator (due to the electrical power used) can (in some smaller cars) easily be enough of the total drag on the engine (at cruising speed) to make a quite noticeable (sometimes even a few MPG) difference in FE.

Originally Posted by Geonerd

Average power draw will be much lower, unless you're trying to induce permanent hearing loss.

Enjoy the music and try not to obsess about the 0.05 MPG you are sacraficing!

While I think the hit on FE is often greater than you are estimating, I do agree that the radio load is often not anywhere near your most significant electrical load on the engine, much less your most significant load on the engine from all sources. And driver comfort is worth something too IMHO.

So while we might disagree "on the numbers", we do agree that it's probably not worth it for someone to sacrifice the radio (assuming it makes their drive more pleasant), just to try to squeeze a little extra FE out of the car. Yes, technically the radio is fully "optional" (in that you don't "need" to run the radio when driving), but it none-the-less can add to driver/passenger comfort at only a small cost (to FE).

Besides which, if saving electricity (in order to get better FE) is the goal here, there are (as I mentioned in my other post) much more effective places (in many cars) to save power (than turning off the radio). For example, both car lights and car fans tend to be real energy hogs in most cars, so anything you can do to lower their power usage (not run them when not needed, switch some car lights to energy efficient LED modules, etc) can make a big difference (likely much more significant than the radio) in total electrical power used in a car.

[Hasbro]

Stereo = 7 lbs. It's in a box.