Mpg goes down while idle

[Fly2High]

That makes more sense to me I don’t see the advantage of seeing that information during idle

why do you keep the trip data up? I always have the gauges display on. Rather see what is going on in the engine than know anything about my trip and economy.

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[Fly2High]

This. Also why ford has added the auto eng cutoff when at full stop. To save gas which does help your overall mpg.

as far as I know, no Mustang does engine cutoff. Is it found on the 150? I would expect it there.

 

[TexasRebel]

does mpg go negative if you drive in reverse?

Absolute values are rough.

 

[Hack]

Great thread! Very entertaining. Thanks, OP.

 

[NoVaGT]

I guess most people disagree but I always thought it was stupid the car keeps calculating mpg while stopped, at least in park. I would hope people understand you are getting 0 mpg while in park with the engine on. I want to know my mpg while actually driving. Especially in the winter, I often have the car ruining while stopped.

I would hope you understand that your MPGs are actually in the negative (not 0), while stopped with the engine on.

If you want to know your MPGs, that's got to be calculated in.

 

[TexasRebel]

I would hope you understand that your MPGs are actually in the negative (not 0), while stopped with the engine on.

If you want to know your MPGs, that's got to be calculated in.

No. They are at 0.
It's an average over the duration of the calculation.
If you drive 50 miles on one gallon and then Idle away one gallon, you've gone 25 mpg.

 

[NoVaGT]

No. They are at 0.
It's an average over the duration of the calculation.
If you drive 50 miles on one gallon and then Idle away one gallon, you've gone 25 mpg.

If you fill up the tank, and drive 0 miles, letting several gallons of fuel burn away while parked, your miles per gallons would be in the negative. It's going to be a negative number, since you burned fuel but didn't move.

I'm not saying that's what the car would register, just what it would be in reality.

 

[atomicpunk]

If you really want to have fun reset the average MPG and coast down a big hill or mountain and watch the crazy #'s you get.

 

[Cobra Jet]

My carton of chicken tenders goes empty when I eat them all..... hmmmm.....

 

[Mr. Met]

If you fill up the tank, and drive 0 miles, letting several gallons of fuel burn away while parked, your miles per gallons would be in the negative. It's going to be a negative number, since you burned fuel but didn't move.

I'm not saying that's what the car would register, just what it would be in reality.

You drive 100 miles and use 5 gallons of gas, what is your mpg?
100 miles/5 gallons= 20 miles per gallon

Now you drive 0 miles and use 5 gallons of gas, what is your mpg?
0 miles/5 gallons= 0 miles per gallon

 

[TexasRebel]

If you really want to have fun reset the average MPG and coast down a big hill or mountain and watch the crazy #'s you get.

ERR DIV/0 isn't really a number though.

 

[ORRadtech]

No, it would not be negative.
It would be 0.
Wouldn't matter if you sat and burned 1 gallon or 200. You would still get zero miles per gallon.
If you took a brand new car straight off the assembly line with zero miles, filled it and let it run you would be at zero miles per gallon.
The only thing that would be negative would be the money in your wallet.

 

[WildHorse]

MPG goes down while you're not moving ? Thanks for the education !

 

[Zrussian13]

I find I can improve the number just by getting off the gas, shifting into neutral and coasting slowly up to the light. As long as you move, keep the rpms low, and reduce the time sitting still, the better your mileage is calculated. Benefits of a manual.

You'll get better mpgs leaving it in gear while you coast to a stop. Once you shift into neutral the computer has to dump fuel to keep it running. In gear the engine continues to spin with the wheels. New cars can go super lean afr while coasting but only in gear.

 

[NoVaGT]

No, it would not be negative.
It would be 0.
Wouldn't matter if you sat and burned 1 gallon or 200. You would still get zero miles per gallon.
If you took a brand new car straight off the assembly line with zero miles, filled it and let it run you would be at zero miles per gallon.
The only thing that would be negative would be the money in your wallet.

Gotcha;

I'm was being stupid. Not thinking things through.

If the car sat and burned fuel, it's not that the MPGs would be negative, because there's no miles to put into the equation as a variable.

But what would be calculated then? GPH? Yes, I think you're then calculating gallons per hour.

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