Excessive Idling and its Effects on Gas Mileage

J

jimm

New member
2007 4Runner 4.0L 6cyl

I know Idling is stupid, but I'm in a strange situation. We have a medical situation and i need to idle a lot while waiting on Boston streets. It's been really cold and no choice.

I know idling uses gas, i had no idea how much. I generally get 19 MPG. With all this idling i just filled up and I'm down to like 10-12 MPG. Yikes!

Does idling really use that much gas? I know I'm not being very specific here. Any one have any idea what the gas drain is while idling?

Thank You.
 
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How long are you idling for??

You've pretty much answered your own question. If the change you have made from averaging 19 to 10 mpg is the idling, then there you go. Are you starting a vehicle cold then just letting it idle? It'll take forever for warm up that way and you'll be sucking fuel. Idling an already warmed up vehicle will use much less fuel, but figure you are achieving exactly 0 miles per gallon while idling, you'll have to switch to something like gallons per hour. I'd imagine idling a warmed up vehicle probably uses 1/4-1/2 gallon per hour of fuel of idling? just a guess.
 
The problem is that idling fuel consumption is measured more like a generator (gallons per hour) rather than mpg since you're not moving. There aren't any real specifications for the 1GR-FE or 2UZ-FE for idling fuel consumption, at least none that I am aware of.

So to say how much fuel your using is hard based on variables.
 
The best estimate I've read is maybe 0.5 - 1 gallons per hour of idling. It's not really affecting your gas mileage, but if you normally get 20mpg and you drive for 20 miles and idle for 1-2 hours then you will measure 10mpg since you used 2 gallons of gas and drove 20 miles. You're still getting 20mpg while driving, but the fuel used while idling is counted too.

Someone on here said idling uses a similar amount of fuel as driving 10mph. Sounds reasonable, and if you get 10mpg driving at 10mph, then that's 1 gallon per hour of idling.

I noticed that the gas gauge and range indicator get confused after long periods of idling, but they read correctly after you drive for a bit.

You can save fuel by reducing the load on the engine. Keep the defroster off since turning it on will run the AC which increases the idle speed (even in the winter). Once the windows are defrosted and the car is warmed up you hopefully won't need the defroster. If you do, you could consider pulling the AC relay to keep it from running (I think it's labeled Mag Clutch or something like that). Note that this will cause an error code to be recorded in the HVAC computer. If you put it on the feet only setting (not feet plus defrost) then I think it blows some air out the defrost vents without running the AC.

Also make sure it's in Park or Neutral not drive so you're not wasting energy in the torque converter in the transmission

If you're idling at home, maybe consider installing a block heater and interior heater, or maybe a remote start. For example, you could install this in the passenger side foot well, plus a block heater for the engine.
https://www.amazon.com/Zerostart-Temro-2600900-Interior-Warmer/dp/B000NM73ZA

Wire the interior heater to a thermostat (located away from the heater) so it doesn't run all the time once it warms up.
https://www.amazon.com/Honeywell-T410A1013-Electric-Baseboard-Thermostat/dp/B01M0DFJ8U/

Then wire the thermostat and block heater to an extension cord to an electrical outlet at your house or work. Keep in mind that this combination draws 1500 W, so make sure the extension cord and circuit you plug into are rated for it. Electricity is cheaper and cleaner than gasoline for the same amount of energy, so this setup could be better than idling if you have a place to plug in.
 
Last edited:
jimm said:
2007 4Runner 4.0L 6cyl

I know Idling is stupid, but I'm in a strange situation. We have a medical situation and i need to idle a lot while waiting on Boston streets. It's been really cold and no choice.

I know idling uses gas, i had no idea how much. I generally get 19 MPG. With all this idling i just filled up and I'm down to like 10-12 MPG. Yikes!

Does idling really use that much gas? I know I'm not being very specific here. Any one have any idea what the gas drain is while idling?

Thank You.
Click to expand...

It's not stupid. I have small children and my rig sleeps outside. When it's 15 degrees outside and they have to go to school, I use my remote starter and let it warm up 10-15 min. I've never heard of "engine damage" b/c of idling, so getting less MPG (your actually mileage doesn't suffer, but you DO HAVE LESS gas in the tank) is just a "deal with it" issue.

BTW, my "mileage" sucks as of late, LOL.
 
motor will still outlast the rest of vehicle

45 years ago my now wife and I had a medical condition (young love) that required hours and hours of idling - never bothered the car, but who cared
 
Technically at idle you are doing 0 MPG, so anything that adds a zero to the mean MPG is going to bring it down a fair bit.

I do it too with remote start, but meh, I get into a warm truck that doesn't have the doors frozen shut.
 
Something to point out, if you're gonna idle the vehicle a lot I do recommend you consider treating the carbon build-up you'll get from the idling.
 
Here's your answer:

I have a scanner/recorder for the T4R from ProScan (OBD-II (OBD2) Scan Tool Software and Hardware).
It is a piece of hardware and a software program for recording the OBDII sensors. I can sit in the 4runner and run it from my Laptop. I know this is geeky.

I measured the MAF (Mass Air Flow Rate) at idle once the engine was at operating temperature. The MAF measured 0.632 Lbs of air intake per minute. Assuming that the air-to-ratio is 14.7 to 1, now I can calculate the fuel consumption, which is 2.58075 lbs of gas per hour. Using the density of gasoline it comes out to 0.41947 gal/hr. Therefore with a 23 gallon fuel tank I calculate one can idle for 54.8 hours. To call it safe round down and assume that you can idle for one day with a half tank of gas and two days with a full tank. That being said, I would never shut the engine off if I were stranded until the second day. But I would climb out to clear the snow away from the exhaust pipe, if it was snowing a lot.
Like

The thread can be found here:

http://www.toyota-4runner.org/4th-gen-t4rs/24717-how-long-can-you-idle-tank-gas.html
 
CookieRoe said:
Great point. Any particular product you recommend?
Click to expand...

I've measured. I was stuck in traffic on an interstate awhile back. Big wrecks, blizzard conditions. Your 4Runner uses about a gallon every three hours, give or take. I had just filled up and got stuck for around nine hours. When finally got going I stopped for food and filled up again just to see. Took about 5 gallons and I had only driven about 20 miles. So 3 gallons in nine hours of idling, or close to it.

Your MPG takes a hit because you get zero mpg when idling. It does not take many zeros to reduce your mpg a lot.
 
I got nothing to help except a funny story about idling.

I asked to borrow a friends Audi B7 RS4. Mildly built breaks, suspension, motor, etc. it's really fun to drive and sounds just pissed off if your idling or on it. Well it's cold out and I was waiting to pick my wife up in the parking lot so I'm just idling waiting. This ecomentalist lady comes up to my window and is insistent that I roll it down. So after my window is rolled down she proceeds to begin to tell me how by idling I'm killing the environment and probably unicorns and stuff like that, quit listening very soon after she started talk about the environment. Instead I blip the throttle and say WHAT I can't hear you over this awesome gas guzzling engine. And then continue to bring it up to about 6k rpm's and back down until she left.

I was laughing so hard by the time she left I was almost crying. My wife then came out and asked if I was trying to get her attention from inside. (It's that loud). I told her the story and she was laughing.


Sent from my iPhone using Tapatalk
 
CookieRoe said:
LOL, yeah, I'm not going to kick my engine's ass. I'm sure a few bottles of fuel injector cleaner would suffice. Just wanted to know which ones (actually work).
Click to expand...

Gotta blow out the cobwebs once in a while. You ain't gonna hurt nothin'...
 
CookieRoe said:
Great point. Any particular product you recommend?
Click to expand...

Eh, I use the "Toyota EFI Cleaner" at work since we have the adapters and we use it for customer cars (hooks into the fuel rail and the vehicle runs off that). It seems to work well, but realistically Seafoam in the gas tank or some similar product is probably going to be the best bet.

If you think you're really carboned up I would:

-Pull the spark plugs, use one bottle of seafoam distributed evenly through all cylinders
-Let it sit a few hours or even overnight.
-Then either blow out the cylinders with compressed air or just crank the engine over with the fuel injection fuse pulled a couple times to blow out any liquid (make sure you do this with the plugs still out so you don't hydro lock it.
-Afterwards, install your spark plugs (if they're very fouled throw new ones in) and run the engine a bit; she'll smoke quite a bit and may run a bit rough, but it should clear up after a bit.

Note- It'd be a good idea to do an oil change shortly after you've done this as some of the seafoam will seep past the rings.

The thing most people fail to realize about seafoam is it works best when you let it soak. There's a guy who did a bore scope comparison when running seafoam through a vacuum line to compare how well it cleans the pistons. The thing is, running it through the vacuum line is more about cleaning the intake not the cylinder tops. The method I mentioned above is how you would clean them up without pulling the head/pistons out and I've done it on a few vehicles with positive results.

But realistically you're not gonna get THAT heavy a carbon build-up on these engines unless you're basically just idling it all the time. So something like Seafoam or a similar injector cleaner in the fuel tank will work best. :) The Toyota stuff we use at work is a bit more concentrated and that's why we hook it up to the fuel rail and have the engine run off of it instead of diluting it in the fuel, but I believe there is also one you can buy from the parts department that goes in the fuel tank.
 
If you're doing this much idling you need to follow the "Extreme Conditions" schedule in the maintenance manual. Your odometer may show that you've only driven 5,000 miles, but your engine has turned revolutions for way more than that. It affects anything "working" while idling. Engine oil, transmission oil, air filter, spark plugs, serpentine belt, etc.
 
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