maxshuty

I thought I'd make this thread to have some MPG myths/truths cleared up.

-First thing I'd like to find out if its true or not is Radio/Music Volume levels. Does playing your radio/cd player at louder levels cause worse MPG? If so how? I dont play mine at extreme ear-killing volumes, but sometimes I do play it on the loud side. Is it true this causes worse MPG?

-Second is 65mph really all that much better than 70mph? Or is 70mph a lot better than 75mph when trying to get 'better' MPG? I ask this because maybe the differences are so small that its not worth being 10, 20, or more minutes late.

Lately I haven't been getting "optimum" MPG, I'm going to go check my tire pressure tomorrow when its warm out! (35* for the high!! )

If you guys could answer these questions that would be great, and anyone else who wants to hijack this thread (as long as it's MPG related questions) feel free to do so

thePH03NIX

hey lately i've been getting really bad fuel economy in my 94 as well...but i know partially is due to my spark plugs needing to be changed, i check every time i fill up and i'm averaging around 12.5 or so, i know another reason it's so low is because of my rear end. i have 3.73 gears...


about what should i be getting? and what are some suggestions to get better MPGs besides changing my sparkplugs

NYstang

yes, 65-75 is a big mpg difference. My families 2003 pilot went form 18mpg to 22mpg when we dropped to 65 for a trip.

Trip with the mustang, did 75 down to PA- 370 miles. got 26mpg. same trip back, 67mph. 30mpg. late fall, so no ac or anything.


once you go over 65ish, you hit a wall and it gets exponentially harder to push faster through it.

AirBrontosaurus

The radio is powered off of the alternator. The alternator is not clutched like the AC, so it is always generating the same amount of power at a given RPM. Whether that power is being used or not is of no consequence to the engine, as it already went through the effort of generating this.

I suppose when listening to the radio, you may drive differently than when you aren't listening to it. However, all things being equal, it makes no difference.

GreyStang

Well, no that's not really true. The more electrical "load" is put on the alternator the more resistance it creates while generating more power, so technically the more power will be required to turn it.

maxshuty

hijacking my own thread! I'm getting 60 miles per quarter tank... That's down from 100mpqt hwy driving. Why? I'm checking my tire pressure tomorrow bit what else could it be? I know it's not my air filter I just put in a k&n air filter

AirBrontosaurus

I would agree with that if the alternator only powered the radio. However, when the engine is running, the alternator is powering the entire car. And, at all times when it's on, it's also recharging the battery. So even when the radio is off the alternator is under load to charge the battery.

Also, you may be right, but why would increased electrical load cause the alternator to take more power to spin? A generator is simply a reverse motor, and the resistance comes from the magnetic coils inside the alternator. The strength of those coils is independent of the power being drawn from the system, so I would wonder how it affects the physical effort to spin alternator.

Using that logic, are you saying that if I continually added more and more electrical components to an alternator, since I am continually increasing the load on the alternator, that it would eventually become impossible to spin? That doesn't seem right to me.

Or, are you saying that the alternator has to work harder to create more power when the load on it increases? I also don't think that's right, because the alternator is not clutched. It's always generating a given amount of power at a given RPM, whether the engine needs it or not. If it cannot supply that much power, it doesn't magically increase it's resistance to make more. It simply doesn't supply enough power.

Or am I misunderstanding you?

Icemizer

Max sound like a winter summer driving issue. When its cold out even with an engine block heater it takes longer for the engine to reach optimum operating temp. In order to get there it has to work harder and consume more gas. Also the entire system must struggle to push the car through the cold/snow. More resistance equals more work equals poorer gas mileage. Adding five or six pounds of ice and snow to your car will increase weight and wind resistance and again the cars mpg will drop.

Brute03

an increased electrical load can in fact cause a decrease in engine efficiency via reduced spark output, however, i don't think the typical stereo system is anywhere near capable of producing such a load.

OP i think your gas mileage went down because most gas stations are using the "winter blend"

Fobra

there is no gain to be had from not listening to the radio... even with the baddest of stereos the difference would be inconsequential