How many gallons are in the tank when the dash "LOW FUEL" light comes on?

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NCSU Dad

NCSU Dad

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Gasoline powered E450 V10 with a 55 gallon tank. The only thing the Ford owners manual says is "refuel as soon as possible".
Also somewhere I remember the gasoline fueled generator will not run when the tank drops below 1/4 tank?

Thanks!
 
Every vehicle is different. If you watch your gas gauge and get a reading as to how many miles you are getting per 1/4 tank on average, you will know about how many miles you have left when you get down to that last 1/8 tank and the light comes on. It's not a perfect science...YMMV, so to speak.
 
This isn't triggered by a standardized amount of remaining fuel, although most independent estimates suggest lights typically engage at 10% to 15% of a tank's capacity. The best way to know for sure is to watch for it and then fill as soon as it comes on. If you do that several times you will get a good feel as it isn't always exactly the same in most vehicles. My son's F350 has approximately 8 gallons in the same size tank.
 
Like it was said, it's model dependant. But the 10-15% of total capacity volume is a good estimate.
 
NCSU Dad said:
Gasoline powered E450 V10 with a 55 gallon tank. The only thing the Ford owners manual says is "refuel as soon as possible".
Also somewhere I remember the gasoline fueled generator will not run when the tank drops below 1/4 tank?

Thanks!
Click to expand...

Yes, that is correct. Most generators "run out" of fuel somewhere around the 1/4 mark on the chassis fuel gauge. The pickup for the generator is set higher than the pickup for the chassis engine so it doesn't leave you without fuel to move the rig.

Try this: When the fuel light comes on, try to fill up (full) as soon as possible. This will give you a general sense of how many gallons of reserve you have before it runs dry. You know the full capacity (55 gallons), so subtract however many you put into it, and that number is your reserve. I like using the "double-click" method. Fill till the pump clicks off. Squeeze the handle one more time. If the tank is full, it should click off right away. If not, it was a false reading and you'll fill till full. Repeat this test a couple of times, calculate the average reserve, and you'll get darn close to your actual reserve number.
 
As said above, it is vehicle dependent. I was told, or read in a manual somewhere on one of my vehicles, that when the light came on, you had approximately 50 miles worth of fuel left.

My personal experience one time was in my 2008 F-250 6.4L diesel. I was pulling my 5th wheel, and I was searching for a Flying J (I had a discount card there). I knew there was one down the road a bit (I-35 somewhere), so I went for it. As the miles went on, I started really worrying that I may not make it. By the time I rolled up to the pumps, I was sweating and my shoulders were tight and sore I was so tense. My tank was a 40 gallon in that truck, and I ended putting right at 42 gallons in it. So I believe it was literally running on fumes. I have never gotten to that point again. I usually fill up at 1/4 of a tank, but I fill up at the first station I can find if I see that low fuel light pop on. I don't want to go through what I did that one time. Too close for comfort.
 
My ‘59 VW Van didn’t have a gas gauge. It had a 1 gallon reserve with a dump valve under the driver’s seat. When it started sputtering you pulled the valve handle and you had ~35 miles to find a dollar.
 
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I understand about filling it up and subtracting that from 55. The low fuel light caught be by complete surprise. The fuel gauge was on the 1/4 mark and next thing I knew the low fuel light was on and the gauge needle was just above Empty. I figure this RV averages 9 mpg so my hope is I have 3 gallons in the tank to get me to the Harris Teeter gas station from home. I was trying to accumulate more fuel points before the fill up. If you don't have a Harris Teeter in your area you can build up points buying groceries to get up to $1.00 off per gallon.

Thanks for the replies!
 
I actually always drive a new to me vehicle to the low fuel warning, just to find out.
When our Sundancer starts flashing the low fuel, I can put 52 gallons in the 55 gal tank.
I've only done that once.
At ~10 mpg, that's not very far.

Our Toad gets ~43 mpg, and has a 15 Gal tank, which flashes the low fuel when it has a gallon left.

Now, in our Lincoln, Which averages 23 mpg on the highway, the low fuel lights up when it says we have 50 miles to go. At that point, I usually get about 11-12 gallons in the fill. At dead empty on the gauge, I can put 13-14 gallons in the 20 gallon tank.
Once, I pushed as far as I could before DW threatened to beat me about the head and shoulders if I did not pull into the next station, and it took a whole 16 gallons.
Those guys believe in safe margins.
 
Our new Chevy almost ran out of gas because the bottom of the tank was a triangular shape. When the gauge hits 1/4 you have to gas up quick. Also many cars have the tank float mounted on a short arm. Above 3/4 and below 1/4 the the angle of the arm causes the gauge to move faster.
 
Guessing the low fuel light anymore is a software point and is only as accurate as the sender in the tank. Mine has only come on once but I was in town and gas was never more than a few blocks away, so I didn't sweat it. Can easily see that on the interstate you might not want to test that feature as the next exit could be beyond the range of that level. In my daily driver I'll run it right down to E just putzing around town but in the RV, anything under half is "get fuel soon". If you run out in the boonies even a 5 gallon can full might not be enough to get you out of a pickle, and would definitely ruin your day. But knowing what the range is when the light comes on is a good data point, if I ever trip mine again I'll try and work that number out.

Mark B.
Albuquerque, NM
 
Speaking solely as truck driver and not a motorhome owner needing gas, in most cases I pretend 1/2" is close to being too empty for my taste. I am also in the came with ethanol gas that the voided region is just a region to generate more dampness with the crap. So I do try to keep my tank as full as possible. It costs nothing extra. And with the HT fuel points, they only allow 35 gallons max, and resets if you get less than the 35 gallons, when you get less at the pump. So I carry five gallon jugs when normally filling up so I maximize the discount. Then I have the cheaper fuel
 
One thing to consider in all of this is that most fuel tanks have some amount of "unusable" fuel in them. In aircraft that's published in the manual, but that means that in a 20 gallon tank you'll run out before you've used all 20 gallons, even if the unusable amount is only half a gallon or so, so you need to be sure to leave a bit of margin.
 
I remember reading a standard on this, I just searched SAE and ISO but came up empty handed but from memory I think minimum one Gallon or 30 miles which ever is greater. if someone has time they may want to do a search. SAE and ISO have websites.
Regards Steven
 
Larry N. said:
One thing to consider in all of this is that most fuel tanks have some amount of "unusable" fuel in them. In aircraft that's published in the manual, but that means that in a 20 gallon tank you'll run out before you've used all 20 gallons, even if the unusable amount is only half a gallon or so, so you need to be sure to leave a bit of margin.
Click to expand...
Larry, is the 'unusable' amount there to collect water that can be drained off? Regards Steven
 
On my 2019 RAM the fuel light icon comes on a little below 100m range remaining. Then around 30m remaining I get "Low Fuel" enunciation. At about 10 miles the range goes blank. I have put more than 26 gallons in the 26 gallon tank.

I've also put more than 18 gallons in my 18 gallon Jeep tank. Missed the exit on my fuel stop at night and the next gas was more than 30 miles away.

Similar thing happened on my MH. First thing happened was the genny quit. I thought, "I should be good to get through Atlanta (heading north) and fuel at the first truck stop. I was mentally calculating remaining gallons and mpg but I was using the wrong total gallons. I am sure I pulled into the pump on fumes.

I normally don't do that. I figure at 1/3 tank I am "on reserve" and need to fill at the next suitable station.

Tulecreeper said:
As my dear old pappy used to say, "Son, it doesn't cost any more to keep your tank full than it does to keep it half full."
Click to expand...

This is true unless you let your 25 year old kid routinely use your truck. I always get it back near empty no matter how much it starts with.

Unless I am going cross country I never put more than 10 gallons in any more. Then he "has" to fuel it - LOL..
 
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