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OK, I know that its actually "0 MPG" because you're burning fuel and not moving, but is there a rough equivalent of a MPG figure when idling? The real figure I'd like to use "gallons per hour" -- but since there's not (as far as I can tell) a cumulative hour gauge for engine runtime, I can't exactly track this figure.

My curiosity is piqued because when I picked the vehicle up new, I reset the trip meter and made a roughly 45 mile trip of urban freeway driving. The tail end of that trip involved a trip to the car wash, and the line was long and very slow due to the pressure washer stage guys taking extra time to blast off ice chunks. I went from ~19 MPG to about ~17 MPG while sitting in the car wash line.

Also, whenever I'm at idle, the instrument cluster "average bar" is always at maximum negative values. I guess this makes sense since I'm not moving at all, but it makes me wonder just how much fuel this vehicle uses at idle. It may just be that the engine/CVT is pretty efficient under way and that in motion the engine speed isn't drastically higher than at idle, resulting in a idle fuel burn that's some substantial percentage of ordinary constant speed.
 

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I believe someone posted in another thread that it burns about .4gph idling. Of course there are several variables that can raise that such as AC. I’d have to do some digging to find the thread. Hopefully someone else will beat me to it
 

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I believe someone posted in another thread that it burns about .4gph idling. Of course there are several variables that can raise that such as AC. I’d have to do some digging to find the thread. Hopefully someone else will beat me to it
Are there any figures of GPH for typical driving speeds to compare it with? I guess I could do the math on MPG, tank size, range and sort that out, but actual numbers someone has read from diagnostics would be better.
 

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You won't be able to tell from the screens how much it's burning because it is calculating based on the current tank of gas and how many miles you have driven on that tank. It you reset it after getting gas, drive 5 miles mostly downhill or coasting, you might show 28 mpg. But then you get stuck at a traffic light and it plunges down to 22 mpg. But, if you had already driven 150 miles on the current tank of gas, you'll probably notice no change in the mpg by idling at the same light.
 

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GPH calculating based on injectors specs ... number of injectors and the time they open ...

time they open can be effected but AC (or any other engine load)

anyhow 2.5L engine normal idle is 0.3-0.5 GPH

2.5L 19 Subaru Forested display calculates 0.439 GPH "saved" for auto stop/start engine
 

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I believe someone posted in another thread that it burns about .4gph idling. Of course there are several variables that can raise that such as AC. I’d have to do some digging to find the thread. Hopefully someone else will beat me to it



Yes, the reading on my Torque App say 0.4gph at idle when warm. Probably more if the engine is cold.


At 60mph the reading is around the 2.5gph mark IIRC.
 
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OK, I know that its actually "0 MPG" because you're burning fuel and not moving, but is there a rough equivalent of a MPG figure when idling? The real figure I'd like to use "gallons per hour" -- but since there's not (as far as I can tell) a cumulative hour gauge for engine runtime, I can't exactly track this figure.

My curiosity is piqued because when I picked the vehicle up new, I reset the trip meter and made a roughly 45 mile trip of urban freeway driving. The tail end of that trip involved a trip to the car wash, and the line was long and very slow due to the pressure washer stage guys taking extra time to blast off ice chunks. I went from ~19 MPG to about ~17 MPG while sitting in the car wash line.

Also, whenever I'm at idle, the instrument cluster "average bar" is always at maximum negative values. I guess this makes sense since I'm not moving at all, but it makes me wonder just how much fuel this vehicle uses at idle. It may just be that the engine/CVT is pretty efficient under way and that in motion the engine speed isn't drastically higher than at idle, resulting in a idle fuel burn that's some substantial percentage of ordinary constant speed.
I'll throw this at you and you can analyze it to your liking:

I put on ~2000mi and the computer logged it at 21.4MPG and my own data shows 20.1MPG. Since you brought this up, I think the difference is likely contributed by the idling (and could be other things) that the computer did not account for the loss while not driving. Based on the math, the difference is ~9gal burned while idling for the ~2000mi total.

You should state your objective, why this super technical detail is important to you.
 

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I did, and you even highlighted in my quoted message. I was surprised to see my mileage drop dramatically from 15-20 minutes of idling.
Oh that's it?!? The 45mi is still considered instant MPG reading, and you might want to log more miles to see a confident trend.

I thought your objective is -something crazy - like compiling data to go after Subaru for the poor mileage (ie 17mpg). And I thought I was the only noob in here that came from analog world.
 

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Oh that's it?!? The 45mi is still considered instant MPG reading, and you might want to log more miles to see a confident trend.

I thought your objective is -something crazy - like compiling data to go after Subaru for the poor mileage (ie 17mpg). And I thought I was the only noob in here that came from analog world.
Yeah, it's admittedly a 50 miles of ownership kind of thing that I don't really worry about. Although as a boat owner, I'm also kind of used to my digital gauges that display gallons per hour and I wish cars had hour gauges and GPH trip computer displays, too.

That being said, while I kind of expected better mileage out of a 2.5L 4 cylinder engine vs. the 4.4L 8 cylinder that was in my previous car, a Volvo S80. It's too soon to pass any meaningful judgements, similar driving has resulted in similar mileage between these cars. But when I look at the basic physics, it's kind of less surprising -- both engines have similar power and similar weight, so from a thermodynamic standpoint it makes sense that they consume a similar amount of energy to do the same work.
 
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