Gas Tank - How low can you go?

[L86 All Terrain]

Just yesterday I put on 650km (403 miles) and put in 83L (21gal) driving pretty hard. Just under 2,000rpm, passed a lot of cars on a one lane highway to a remote jobsite. Works out to 12.6L/100km or 18.66 us mpg. Drove more that day, but that was just one fill that I recorded. Worked a 12hr day in the bush the same day to, 21hr work day, good thing I am off today lol. That 83L was about 1/8th of a tank on the gauge, no fuel light. Most I have jammed in a K2 is 88L.

[Grumpy Bear]

Half a tank gets me to the pump. Fill till it shuts off then wait a few seconds and give in one more to the auto shut off. That last half is for pump cooling and emergency use. Like some greedy station wants the kings ransom and thinks I can't make it another foot without them. 

[Ravenkeeper]

On 5/2/2018 at 4:01 PM, Ravenkeeper said:

I can usually get another $2 into it, but I usually squeeze another $1 and change, up to the next whole dollar, into it.  If you're not consistent with first click, or next click, then things like Fuelly will be "off."  Truck computer (Trip B) shows AMPG as 19.3, since I bought it.  I reset Trip A at every refuel, and the computer varies 0.2-0.9 against Fuelly, per fill-up, because of the way I fill it up.

 

On 5/2/2018 at 3:54 PM, Ravenkeeper said:

I've had the light come on a few times.  One time, I rolled up to the pump with 0 miles remaining, for about 10 miles (base gate to gas station).  Not saying to push it to the limit, but sometimes, you can get lucky stretching it to the pump.  I knew it was going to be close, so I had my lawnmower can with me, with some fuel in it, in case I heard it start to sputter.  I normally gas up around 1/4-1/8 tank left, but definitely every Sunday, on the way home from church. 

 

I've done it twice, that I can see on my Fuelly account, since the above postings, May 17th (432 miles) & 29th (437 miles), the gas stations I used, those times, would only allow me to gas up to $75.  YES, I filled up this morning with "FUEL LOW" showing on the DIC.  The crazy part of this last one, I pulled into Stater Bros, in Mojave, with light on and "49 MTE," when I started my truck to go home..."FUEL LOW."  WTH?!!!  I can understand the display going to "FUEL LOW" when the computer gets to 10 or less, but with an estimated 49MTE?  REALLY?!!!  That's as bad as going down a hill, with just over a 1/4 tank, watch the MTE roll down to "FUEL LOW," and then stays that way, sometimes until I refuel. 

[busydaddy]

Towed our camper a couple weekends ago. I was waiting to cross the state line before filling up but 7-9 mpg always makes things interesting. I hit my new high (low) of 24.5 gallons.


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[CadillacLuke24]

I'll fill up when the light comes on. It's pretty accurate, I've traveled with my destination being mere miles less than the Range showed, and have made it there without running out (once I get there I will fuel up immediately). Dad gets a dollar off at Smith's, so we try to capitalize on that. I'll try and get as much as I can in. I've only overfilled a handful of times, which results in an immediate trip to the car wash for the left bedside.

 

I think the most I've gotten in is 27.3 gallons, though as of late I've been less eager to do that due to the evap system (no check lights yet, but I don't want to chance it). That being said, I've gone 560 miles on a tank before. It's nice to have the extra range when you need it. 

[swathdiver]

On 5/2/2018 at 7:01 PM, Ravenkeeper said:

I can usually get another $2 into it, but I usually squeeze another $1 and change, up to the next whole dollar, into it.  If you're not consistent with first click, or next click, then things like Fuelly will be "off."  Truck computer (Trip B) shows AMPG as 19.3, since I bought it.  I reset Trip A at every refuel, and the computer varies 0.2-0.9 against Fuelly, per fill-up, because of the way I fill it up.

Fuelly isn't very smart in its calculations.  First, it does not give the option of calculating for actual fuel used, it assumes what you pumped is what you used.  Second, it calculates the stats based on the last tank with the prices just paid for the new tank.  In the grand scheme of things it's only a few cents a mile off but such adds up over time.  I like it, just needs improvement.

[Grumpy Bear]

Okay I tried it but remember I'm handicapped by my RCSB little 26 gallon tank. 718 miles and the low level light is not yet on. The needle is just below 1/8th. 

 

UPDATE: Low Level Light comes on at 23.9 gallons consumed by Scan Gauge II (calibrated) and gave 726.9 miles this tank. 

[swathdiver]

My tank is rated for 31.5 gallons in some literature, the Tech2 lists it as holding 31.2 gallons.  The average fill before clicking full is 26 gallons and the most ever was 28.  If the front of the truck is level or slightly down it will take on less fuel than if the nose is slightly raised.  Filling from a level position the Tech2 will read 98% full and once you pull onto the highway it will read 85-88%.

[Nick The Great]

My lowest for this truck is 21.29 gallons.  And if I remember right, that made me really nervous.  

 

I've never run out of fuel in my life and I ain't about to start now! 

 

My 2007 I put over 24 in a few times, and that wasn't my idea!  

[Hoginedgewood]

Gas cools the pump, so by pushing the limits you’re overheating the pump. It’s good to know what you can get by with, but don’t on purpose.

[Camaroboi13]

I've put 22 and change on mine, didn't want to push it but I forgot to get gas on my way to work so once the light came on I drove another 39 miles to get back home.  I don't exit my vehicle to and from work for security purposes, otherwise I would have gotten gas sooner.  It was definitely the quietest trip home I've ever made!

[Grumpy Bear]

10 hours ago, Hoginedgewood said:

Gas cools the pump, so by pushing the limits you’re overheating the pump. It’s good to know what you can get by with, but don’t on purpose.

Yes it cools the pump but in tank pumps are not new and they will take more than you think they will. I've run one vehicle to the low level light for 200K without issue and it took 145K to kill another. Don't make it a practice but it isn't like it will puke after a few trips to the light either. No need to yell fire in a full theater.  

[Supreme Pizza]

I could be wrong, but I do not believe that the pump will overheat from low fuel. The pump is not cooled by sitting in a bath of fuel, the fuel passing through the pump is what draws the heat away from the electric motor. If you run out of fuel, and the pump keeps running, then it will overheat. It would be like losing all the coolant in your gas engine. If your truck dies because it ran out of fuel, you should shut the key off right away to shut the fuel pump down. 

 

Interestingly enough, after researching it a while back -  it turn out that there is not enough oxygen in a fuel tank for combustion. So if the fuel pump were to short out and throw sparks, under most conditions there would not be a fire or explosion. 

[ChristopherDB]

I doubt running low affects the long term life of the pump. I'm just basing that on every vehicle I own I've constantly had habit of running on fumes and never had any issues. I hate going to the gas station! As startman8tdc mentioned I think it's the flow of fuel that cools the pump moreso than it sitting in the fuel, which down here in Florida is probably not very cool. as long as the truck is running, fuel is flowing. 

 

I've seen bildge pumps run dry for hours and still work. I'd be more concerned about picking up all the sediment at the bottom if the truck is old and getting into the impeller. 

[2018GMC]

I would think current trucks and cars can tolerate low fuel and not destroy pump.

 

My 1997 GMT400 generation is on its 3rd fuel pump at 208k. This generation is known to eat fuel pumps. I try and keep it 1/4 tank or more. Last fuel pump change was because of sending unit not being accurate. When I pulled the pump / sending unit you could see where it was shorting out on certain areas of the sending unit. I know this generation had a constant loop of fuel being returned to tank. I thought newer vehicles regulate fuel pump pressure by rpm so the pump is not constantly running wide open circulating fuel.

 

I know the K2xx has 2 fuel pumps. One low pressure lift pump in the tank and another high pressure 2k psi under the intake manifold for the DI engine.