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4x4tographer

How Long Can Your Vehicle Idle (for warmth?)

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For some reason, my mind was unusually active last night and I was thinking about those poor folks stuck out on the I-95 in Virginia in a blizzard.

 

It got me to thinking about if I managed to get stuck out on a trail overnight in the cold, and the hypotheticals around being forced to sleep in my Jeep overnight in sub-zero. How long can my specific rig run to keep the heat on?

 

I came across this pretty nice article that pretty much answers the question for you. Through a Canadian agency, they were able to determine the average vehicle has a burn rate per liter of displacement of 0.6 liters per hour. 

 

You can do the math manually, but I put together a quick little calculator on Google Sheets to help out. 

I also added in a "fuel level" input to help you guesstimate your approximate idle time at different tank levels.

 

 

1206594829_ScreenShot2022-01-13at9_21_02AM.png.93b0d5adda00a0f1c4d0015a964d0cd6.png

 

In my particular case, my 3.6L 2018 JLU has a 21.5 gallon tank. If it was 100% full, I'd get about 37 hours of idle time out of it.

 

Note that these are just "guesstimates". Your actual idle fuel consumption might be different based on a variety of factors such as modification, fuel types, programming, etc...

As this is a hypothetical "survival scenario" its worth mentioning that you can run the risk of engine damage as well by idling for extended periods.

 

CLICK HERE for the calculator

(You can only edit the white cells, anything in blue is locked/formulae)

Edited by 4x4tographer
Forgot to link to the article!
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very interesting!

 

so our 3.6L engines (if they are close to that average) would use just over a half gallon per hour at idle.

 

one blog author said his JK Wrangler would use "at least" 2.5 gallons to idle 8 hours, which is only 0.31 Gallons/hr - but no idea how he came up with that number.

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also worth mentioning here, a few people die every year from carbon monoxide poisoning while sleeping in an idling car. a modern vehicle in factory condition, in a wide open area, is NOT likely to kill you... however, if you have a header leak or a mid-vehicle turn-down exhaust and are stuck in the snow or mud the wrong way, or experience some other weird combination of factors - it could happen, so be aware!

 

i always recall this tragic news story when i think about idling for a long period.

 

 

Edited by theksmith
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21 minutes ago, theksmith said:

very interesting!

 

so our 3.6L engines (if they are close to that average) would use just over a half gallon per hour at idle.

 

one blog author said his JK Wrangler would use "at least" 2.5 gallons to idle 8 hours, which is only 0.31 Gallons/hr - but no idea how he came up with that number.

 

That's interesting! Just ran the math on that (provided I didn't screw anything up), that rate of .31 gal/hr is about 45% MORE efficient than the Canadian's wager. 

 

Of course, so much comes into play. Altitude is another factor I didn't think of initially, for example.  I'm betting the 0.6 L per L of displacement is just a "rule of thumb" figure.

 

I wonder if there is a way to pull fuel consumption figures via the ODBII and a reader to hone in on your specific vehicle at idle. For example, run the vehicle for 10 minutes, see what the consumption rate is then multiple by 6 to get the hourly burn rate!

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Added in a box that converts your fuel burn rate from L/hr to Gal/hr because 'Murica.

 

843021196_ScreenShot2022-01-13at10_40_19AM.png.6c9fa12f37d0f8619f7243d713f0ddee.png

 

Also found some US gub'mint statistics from 2015 that shows idle consumption rates for various sized vehicles and fuel times. 

 

The note that their Large Sedan figures is a 4.7L engine, and the Medium Heavy Truck is 5L to 7L (these figures are in a table at the above link).

 

Based on that, if we split the difference (given many of our rigs are of the 6 cylinder variety), the above burn rate of 0.57 gallons per hour doesn't seem too far off in my opinion.

 

fotw861.jpg?itok=MXyf4veC

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On 1/13/2022 at 9:33 AM, theksmith said:

very interesting!

 

so our 3.6L engines (if they are close to that average) would use just over a half gallon per hour at idle.

 

one blog author said his JK Wrangler would use "at least" 2.5 gallons to idle 8 hours, which is only 0.31 Gallons/hr - but no idea how he came up with that number.


My guess would be the Engine Run Time timer on the EVIC. On the JKs with the advanced EVIC, it's part of the normal data rotation and can be reset by a long press of the Enter/OK button. On the older JKs, with the basic dash, it's in the RPM display rotation and can be reset by holding the rotation button down for an extended press.

On the JL and JT, engine run time is part of the A/B trip counters.

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On 1/13/2022 at 9:38 AM, theksmith said:

also worth mentioning here, a few people die every year from carbon monoxide poisoning while sleeping in an idling car. a modern vehicle in factory condition, in a wide open area, is NOT likely to kill you... however, if you have a header leak or a mid-vehicle turn-down exhaust and are stuck in the snow or mud the wrong way, or experience some other weird combination of factors - it could happen, so be aware!

 

i always recall this tragic news story when i think about idling for a long period.

 

 

 

Having lived temporarily out of a vehicle in colder weather, it was then and still is now my policy that I run the vehicle, get it nice and toasty (hot as I can really), turn it off, sleep until the cold wakes me up, rinse lather, repeat. The sleep isn't great, but it beats permanent sleep. I have this policy regardless of new or old vehicle. I do just cannot bring myself to trust being anywhere near emissions and an enclosed space.

It is really worth noting that we drive vehicle we abuse to put it nicely. So aside from any potential manufacturer defects in the exhaust pipeline, consider leaks we put in that pipeline with the rocks we drive our vehicles over. I know the resonator approximately under the back seat of my 1yo 2020 gladiator has the ever living crap beat out of it from the last ledge on the Backway to Crown King. 

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Like water in the Arizona summer I would toss a sleeping bag into my rig if I lived in the snow.  I do this if I am wheeling somewhere I might end up spending the night (rig breaks down) and it was going to be cold. 

 

Carbon monoxide detectors are cheap.    Probably wouldn't be a bad idea to have one if there is a possibility you'll be trapped in a cold traffic jam like the one mentioned, even if you are not planning on sleeping. 

 

Just some thoughts.    Good subject!

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