how is fuel tank level calculated?

[JeffN]

My light came on yesterday and this morning I went out to fuel up. The range said “Low” and the gauge was pegged on E. This was odd to me because the light came on as I was about a mile from home last night, I didn’t drive around with the light on. I filled up and it took just 23 gallons (3500 w/32 gallon tank.) I hit the nozzle a few more times and the tank was indeed topped up.

I have been towing on and off for the last 2 weeks, so my MPG has been all over the map. I assume range is calculated dynamically based on average mpg, but does the fuel gauge read the actual fuel level or does it read the range and adjust to reflect estimated remaining fuel?

 

[Quyonmob]

Gauge reads purely the level in the tank. Range is the one that fluctuates add you mentioned.

Odd it was pegged on E with 9gal still in there. I pegged my 1500 on E with “low” as range and I pumped 81L into an 80L tank when the handle clicked off.

 

[JeffN]

that is what I would expect. I can’t explain why the gauge was fully on E with 9 gallons remaining.

 

[SniperDroid]

Were you parked on a slight slope?

 

[BWL]

That was a problem on the 1500s with the larger tanks, but first I've heard of it on the hd trucks. On the 1500s the fix was just a software update. Wonder if something is set up wrong in the ecu.

 

[TestPilot57]

I pegged my 1500 on E with “low” as range and I pumped 81L into an 80L tank when the handle clicked off.

that is what I would expect.

It's what I have always experienced on any other vehicle I've owned.

But on my second RAM this has never been the case. Both have had the oversized tank and I have done all the recalls/updates.

Though I've never had 9 gallons left, I typically fill up within 20 miles of the light coming on* with a range of 30-50 miles at fill-up, and usually an EVIC Avg MPG of 14-15. I can rarely get 26 gallons in, which leads me to believe that there is a 3-4 gallon cushion.

*In winter I try to fill up before the light comes on, because Remote Start won't work if the light is on. One of my pet peeves...

 

[KeithP]

Probably going to hammered for this, but I never understood the concept of waiting until the low fuel light or x miles to empty before filling up. I taught my kids that it doesn’t cost any more to keep the top half of the tank full than the bottom half. Empty tanks draw condensation and worrying about gas if you get caught in traffic, a bad storm or any other unfortunate event is virtually eliminated.

Not saying I’ve never seen my gauge below half, but it is rare that I do and it’s never for very long.

 

[VStan]

that is what I would expect. I can’t explain why the gauge was fully on E with 9 gallons remaining.

I'm only at 627 miles on my 2021 Ram. Coming home yesterday I could't figure out why my range was 167 miles but I was nearly on empty. Then it passed what I THOUGHT was the empty mark and I had a good laugh at myself. I could only see the true empty mark if I leaned forward and looked directly at the gauge. Sure enough, when I got gas it took 22 gallons of the 33 gallon tank and all calculations came out right. So 11 gallons left with a couple for reserve comes out about right.

 

[BWL]

I like to see how far I can push it. My tank holds 121l as far as I know, but the most I've managed to pump in is 117l. That last 4l takes more bravery than I have I guess. One day. Fine line between failure and glory.

 

[Daw14]

Everyone should keep in mind that the fuel in the tank is what cools the fuel pump, running low all the time will shorten the life of that pump

 

[Jimmy07]

Everyone should keep in mind that the fuel in the tank is what cools the fuel pump, running low all the time will shorten the life of that pump

Internet myth. It’s just like any other pump motor (fuel, sump, or otherwise)- it is the fuel running THROUGH the pump, not the fuel sitting AROUND the pump, that cools it. By your theory, given the height of the pump, you should never let the fuel level get below 3/4 tank.

 

[Jimmy07]

My light came on yesterday and this morning I went out to fuel up. The range said “Low” and the gauge was pegged on E. This was odd to me because the light came on as I was about a mile from home last night, I didn’t drive around with the light on. I filled up and it took just 23 gallons (3500 w/32 gallon tank.) I hit the nozzle a few more times and the tank was indeed topped up.

I have been towing on and off for the last 2 weeks, so my MPG has been all over the map. I assume range is calculated dynamically based on average mpg, but does the fuel gauge read the actual fuel level or does it read the range and adjust to reflect estimated remaining fuel?

I’ve had the same issue on my 2017 2500 since day one brand new (mine is the 6.4 with 31 gallon tank). Pegged past E, range showing low, 24.5 gallons will top it off. I’ve tested numerous times with a gas can that I can go another 100 miles once the fuel range shows “low”. I’ve tried changing every fuel related value in the BCM with AlfaOBD, and nothing changes/corrects what the gauge is reporting.

 

[JeffN]

first, everyone has different circumstances they deal with. If I’m driving through Oklahoma, diesel is readily available but here in the Bay Area, I have to be strategic about filling up because I try to avoid stations that don’t turn their diesel tanks frequently. And maybe 1 in 7 stations even has diesel.

In this particular instance, I didn’t purposefully wait until the light went on and with 30% of the tank capacity remaining, I should have had another 100 miles of range.

Read the context of what I wrote in my original post. FWIW, I also park my vehicles nose out, have my bug out bag and trauma bag in the front hall closet, and ammo stash in multiple locations.

Probably going to hammered for this, but I never understood the concept of waiting until the low fuel light or x miles to empty before filling up. I taught my kids that it doesn’t cost any more to keep the top half of the tank full than the bottom half. Empty tanks draw condensation and worrying about gas if you get caught in traffic, a bad storm or any other unfortunate event is virtually eliminated.

Not saying I’ve never seen my gauge below half, but it is rare that I do and it’s never for very long.

 

[Zoe Saldana]

Probably going to hammered for this, but I never understood the concept of waiting until the low fuel light or x miles to empty before filling up. I taught my kids that it doesn’t cost any more to keep the top half of the tank full than the bottom half. Empty tanks draw condensation and worrying about gas if you get caught in traffic, a bad storm or any other unfortunate event is virtually eliminated.

Not saying I’ve never seen my gauge below half, but it is rare that I do and it’s never for very long.

It also is a safe practice. Fill up in daylight and not at night when you might get robbed or jacked.

 

[TestPilot57]

...it doesn’t cost any more to keep the top half of the tank full than the bottom half.

Yes it does (unless you mean only filling half way when it's empty, but I would never do that).

It takes the same amount of time to pull in, get out, run your card, put the nozzle in, press start, top up the nickel or whatever you do, put the nozzle away, put the cap back on, get in and pull out whether you're getting 1 gallon or 100.

Time can't be bought, and they aren't making any more of it anyways. If I can eliminate 10 fill-ups a year and it saves me just 3 minutes per time, that's a half an hour a year. Even if all I do with that 30 minutes is surf the ramforum, I feel it's worth much more than doing nothing at a filling station.

 

[Zoe Saldana]

Yes it does (unless you mean only filling half way when it's empty, but I would never do that).

.

No he doesn't.

 

[Quyonmob]

Probably going to hammered for this, but I never understood the concept of waiting until the low fuel light or x miles to empty before filling up. I taught my kids that it doesn’t cost any more to keep the top half of the tank full than the bottom half. Empty tanks draw condensation and worrying about gas if you get caught in traffic, a bad storm or any other unfortunate event is virtually eliminated.

Not saying I’ve never seen my gauge below half, but it is rare that I do and it’s never for very long.

gas stations were 600km apart where I was when I ran mine to the peg.

I never go below 1/4 tank intentionally.

 

[KeithP]

Yes it does (unless you mean only filling half way when it's empty, but I would never do that).

It takes the same amount of time to pull in, get out, run your card, put the nozzle in, press start, top up the nickel or whatever you do, put the nozzle away, put the cap back on, get in and pull out whether you're getting 1 gallon or 100.

Time can't be bought, and they aren't making any more of it anyways. If I can eliminate 10 fill-ups a year and it saves me just 3 minutes per time, that's a half an hour a year. Even if all I do with that 30 minutes is surf the ramforum, I feel it's worth much more than doing nothing at a filling station.

Thirty minutes of time is cheap insurance against being stranded in a traffic jam or storm with an empty tank.

 

[JeffN]

feel free to debate the merits of refueling frequency, I’m just trying to figure out why my truck was telling me I was empty and not even computing range when I had 9 gallons of fuel still in the tank. I looked up my VIN and Ram is telling me there are no updates but it sounds like other owners have had this problem. I guess I’ll have to go to the dealer and have them tell me there is nothing wrong with my truck.

 

[KeithP]

feel free to debate the merits of refueling frequency, I’m just trying to figure out why my truck was telling me I was empty and not even computing range when I had 9 gallons of fuel still in the tank. I looked up my VIN and Ram is telling me there are no updates but it sounds like other owners have had this problem. I guess I’ll have to go to the dealer and have them tell me there is nothing wrong with my truck.

Yup this took a left turn. My apologies for my part in that. Also sorry I don’t have an answer for your problem.