Fuel Tank Capacity - Low Fuel Light

[shokker70]

Exactly, wife sez "why are you always looking at that crap, you got your JT". I respond with "I'm learning"

That's too funny. My wife said almost the exact same thing the other day. Now she just thinks I'm looking for ways to spend money.

Funny again I found this thread today. The low fuel light came on this morning as soon as started up. Was wondering just how far I might make it. 36 miles door to door going to work. Hit the low fuel warning just before pulling into the gas station maybe 5 miles from the office. 19.7 Gal. Maybe I could have squeezed a bit more, but didn't try.

For the initial low fuel light, I've seen what others are reporting, close to 18.5 gal to fill back up.

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[PyrPatriot]

Cool. I wish the tripometers would show how many gallons we have used since rezeroing them in additional to the other things. Some of my previous vehicles did that. I could zero after filing up, and assuming the tank-capacity spec was correct, know how much I had remaining.

The low fuel light is supposed to come on when you have 2 gallons left. When it comes on you should be able to put in 20gal of gas into the tank, probably a little more. But so far I've only ever had 18gal fit in when I run it that low (without manually adding more gas) It clearly comes on well before that because even with wiggle room of the estimated mpgs/miles remaining I drove well past 2 gallons of gas.

On that note, despite not changing my driving habbits I have gone down from 22mpg when I first bought the JT to barely 17.5. Granted I'm taking fewer longer trips (100mi each way) and most of my driving is city, but little of it is in rush hour traffic. Makes me wonder what is going on. I re-set the mpgs for each fill up but leave the life-time mpg tracker unchanged (Trip B)

 

[ShadowsPapa]

When it gets warmer I have no problem throwing a gerry can in the back and driving 30 miles past "0 miles to empty" to see what happens. It's so new I'm not going to "suck up junk" floating on the top of the gas at this point, which is what the internet would have you believe happens. My wife has run our LR4 out of gas no less than 3 times and I had to come with a can. No effect on the fuel pump, etc.

I've worked on more fuel systems than almost anyone writing that BS out there about gasoline and fuel tanks. I've pulled tanks from cars 40 years old - nothing in but gas. The worst that can happen running an electric pump dry is damage to the pump - but NOT from stuff in the tank, but from it running dry. And even that varies with the pump and type.
Doesn't matter if your truck is 1 month old, a year old or a decade old, unless you buy really crappy stuff - your tank will be without stuff floating or even swimming around in it. No chunks. Besides, there's a good "nylon sock" or other filter type in there..............

 

[ShadowsPapa]

I get the impression that the Range feature, as with other vehicles, tells you the max of how much further it thinks you should go before you should filling up the tank again, not how many miles you actually can go before the tank completely runs dry. Until someone completely runs their tank dry, we will never know. Any volunteers?

Silverado and Grand Cherokee - that darned thing is quite accurate. I recall when my wife's Jeep said low fuel, and we calculated when it came on, and how far we'd driven. I did the math and figured they may be half a gallon in there......... I got the full tank capacity in it when we finally filled up - she was upset I kept saying we're ok, we're ok, hit the next station. She said - see, we were NOT ok!
I was damned lucky, that's for sure. That thing was accurate.
Similar for my Chevy - if it said you had xx miles left, you did the math and could figure about how much you could put in there and it was within a gallon each time.
It also tracked the gas used.

 

[Tim]

The low fuel light is supposed to come on when you have 2 gallons left. When it comes on you should be able to put in 20gal of gas into the tank, probably a little more. But so far I've only ever had 18gal fit in when I run it that low (without manually adding more gas) It clearly comes on well before that because even with wiggle room of the estimated mpgs/miles remaining I drove well past 2 gallons of gas.

On that note, despite not changing my driving habbits I have gone down from 22mpg when I first bought the JT to barely 17.5. Granted I'm taking fewer longer trips (100mi each way) and most of my driving is city, but little of it is in rush hour traffic. Makes me wonder what is going on. I re-set the mpgs for each fill up but leave the life-time mpg tracker unchanged (Trip B)

Do you let your JT warm up on cold mornings? My fuel milage always goes in the crapper in the winter just for that reason. Also, you are probably using a "winter blend" gasoline during the colder months. Winter blend gas is less efficient than summer blend gas.

 

[PyrPatriot]

Do you let your JT warm up on cold mornings? My fuel milage always goes in the crapper in the winter just for that reason. Also, you are probably using a "winter blend" gasoline during the colder months. Winter blend gas is less efficient than summer blend gas.

Yes mpgs go down in cold weather but it has just now gotten cold and I have been at 17-18mpgs from 65 to below freezing. I got a 1-2mpg boost adding half a tank of ethanol free gas. I dont know about winter blends of gas

 

[ShadowsPapa]

Yes mpgs go down in cold weather but it has just now gotten cold and I have been at 17-18mpgs from 65 to below freezing. I got a 1-2mpg boost adding half a tank of ethanol free gas. I dont know about winter blends of gas

That's because it's not something consumers are told about because it's automatic and you can't buy one or the other - you get what is in season in your area. You can't ask for one or the other.
Winter blend is different in the "high parts" that evaporate in heat. Summer blends have FEWER high parts, winter blends get the high parts because it's necessary for the fuel to easily atomize or break-up in the winter.
That's not necessarily what's doing it.
There's not a huge difference - less than 2% energy difference between winter and summer.
The EPA says conventional summer-blend gasoline contains 1.7 percent more energy than winter-blend gas, which is one reason why gas mileage is slightly better in the summer.

Cold weather and winter driving conditions have a bigger impact.
From AAA -
Fuel economy tests show that, in short-trip city driving, a conventional gasoline car's gas mileage is about 12% lower at 20°F than it would be at 77°F. It can drop as much as 22% for very short trips (3 to 4 miles).

 

[WhatExit?]

So, after all this I'm still left wondering/asking...how accurate is the RANGE (miles remaining)?

My Honda Accord has an excellent range report that's super accurate so I can count on that to be correct while I'm desperately looking for gas.

I hope to learn about the Gladiator's RANGE accuracy as we go off roading in Death Valley and numerous other remote areas and even with gas cans and good planning it can still get just a bit hairy figuring out if we can make it to the next station (and what time it's open 'til nevermind that it's over $5.00/gallon).

 

[PyrPatriot]

So, after all this I'm still left wondering/asking...how accurate is the RANGE (miles remaining)?

My Honda Accord has an excellent range report that's super accurate so I can count on that to be correct while I'm desperately looking for gas.

I hope to learn about the Gladiator's RANGE accuracy as we go off roading in Death Valley and numerous other remote areas and even with gas cans and good planning it can still get just a bit hairy figuring out if we can make it to the next station (and what time it's open 'til nevermind that it's over $5.00/gallon).

Let's put it this way. I got to where the Range estimated left was 15 miles for 12 miles before going down to 10mi left on the range.My average MPGs did not change during that time period.

 

[Gatorized]

Cold weather and winter driving conditions have a bigger impact.
From AAA -
Fuel economy tests show that, in short-trip city driving, a conventional gasoline car's gas mileage is about 12% lower at 20°F than it would be at 77°F. It can drop as much as 22% for very short trips (3 to 4 miles).

That lines up with my observations during my morning and evening commute... always have a tough time getting the mpgs up where I like in the AM. And the PM always exceeds my expectations!

 

[tweak89]

This has been bugging the crap out of me!! Was about to start a new thread and this one came up. If I stop to fill my tank within a few miles of the low fuel warning I can only ever put in around 18 gallons. I usually get a 24-30 mile countdown once the low fuel light comes on, but have taken it up to 25 miles past "0". I found it strange that it comes on so early, I even called my dealer to confirm that our tanks are actually 22 gallons.

 

[PyrPatriot]

This has been bugging the crap out of me!! Was about to start a new thread and this one came up. If I stop to fill my tank within a few miles of the low fuel warning I can only ever put in around 18 gallons. I usually get a 24-30 mile countdown once the low fuel light comes on, but have taken it up to 25 miles past "0". I found it strange that it comes on so early, I even called my dealer to confirm that our tanks are actually 22 gallons.

The VERY first fillup my JT had (after test drive) the range estimator had 440mi at 19mpg. Which means there was 23gal in the tank. So there CAN be some variation. What concerns me is when the low fuel light comes on, because that is supposed to be at a VOLUME of fuel remaining. So if you fill it up when it comes on you should be getting 20gal of fuel in easy, not 18gal.

 

[MarineHawk]

The VERY first fillup my JT had (after test drive) the range estimator had 440mi at 19mpg. Which means there was 23gal in the tank. So there CAN be some variation. What concerns me is when the low fuel light comes on, because that is supposed to be at a VOLUME of fuel remaining. So if you fill it up when it comes on you should be getting 20gal of fuel in easy, not 18gal.

I am reading what appears to be an assumption by numerous people on here that the vehicle computer is estimating your Range based on the MPG reading on the Fuel Economy display. I don’t think that’s true for a variety of reasons.

For example, you can reset/zero your Fuel Economy MPG reading by holding down the OK button while in the Fuel Economy display. One time, it was reading around 12 MPGs after I zeroed it and had then driven around town in rush hour for days. I reset one of the trip meters after filling up the tank and as I was headed out on a highway road-trip. I then zeroed the Fuel Economy MPG reading once on the highway. It started reading around 21 MPGs. However, the “Range” reading did not change at all based on my mileage going from 12 to 21 MPGs. If the computer was calculating my Range based on the MPG reading, it would have instantly gone up 75%. It didn’t do that.

My Range reading does change though, over time, as I’m getting better or worse mileage. I think it does not calculate that based on the visible reading on the Fuel Economy display, but rather based on what you’ve been getting over the last 50 miles or something like that. It doesn’t happen suddenly, but it obviously is taking account recent driving conditions.

EDIT: FWIW, the Manual has this to say:

"Range – The display shows the estimated distance (mi or km) that can be traveled with the fuel remaining in the tank. When the Range value is less than 10 mi (16 km), the Range display will change to a 'LOW' message. Adding a significant amount of fuel to the vehicle will turn off the 'LOW' message and a new Range value will display. Range cannot be reset through the OK button."

 

[WhatExit?]

EDIT: FWIW, the Manual has this to say:

"Range – The display shows the estimated distance (mi or km) that can be traveled with the fuel remaining in the tank. When the Range value is less than 10 mi (16 km), the Range display will change to a 'LOW' message. Adding a significant amount of fuel to the vehicle will turn off the 'LOW' message and a new Range value will display. Range cannot be reset through the OK button."

Thanks - good info. This makes me wonder (not sure if it was mentioned in the previous posts)... how much gas can be put into the tank (on a fill-up) once the LOW message comes on?

 

[PyrPatriot]

My Range reading does change though, over time, as I’m getting better or worse mileage. I think it does not calculate that based on the visible reading on the Fuel Economy display, but rather based on what you’ve been getting over the last 50 miles or something like that. It doesn’t happen suddenly, but it obviously is taking account recent driving conditions.

EDIT: FWIW, the Manual has this to say:

"Range – The display shows the estimated distance (mi or km) that can be traveled with the fuel remaining in the tank. When the Range value is less than 10 mi (16 km), the Range display will change to a 'LOW' message. Adding a significant amount of fuel to the vehicle will turn off the 'LOW' message and a new Range value will display. Range cannot be reset through the OK button."

I base the estimate on the total life MPG of the vehicle. I have never reset Trip B, which means it shows the lifetime fuel economy and odometer of the vehicle. I understand what you are saying about how your mpgs can vary and thus your fuel economy estimate can change. My point is that I have had several instances where my mpgs didn't change and my remaining miles didn't change once the low fuel light came on; at least the estimate didn't change for several miles (i.e. saying I had 45mi left for about 20mi, then dropping down by like 5mi, 20mi, etc).

Regarding the LOW status, that is another bone I have to pick. If 10mi are left, then at BEST it can have about 1/2 gal left in the tank. I have run it a few miles AFTER it reached the LOW indication and still only refilled 19-20gal, which means as always, I am 2gal away from filling tank capacity, which should not happen.

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