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Upgrading to larger fuel tank 2021 F-150

dkt

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Just brought a 2021 with 36 gallon tank. Hit 8 miles to empty fill up only took 31 gallon at fill up. Average 20.5 per gallon only went 618 miles 36 gallon should of went over 720 miles
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Subhunter

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Just brought a 2021 with 36 gallon tank. Hit 8 miles to empty fill up only took 31 gallon at fill up. Average 20.5 per gallon only went 618 miles 36 gallon should of went over 720 miles
I've not run my tank below 1/4 tank but noticed the same thing DTE never shows anything over 700, highest I have seen was 660. Is it possible the truck does not know what size tank it has?
 

Missmy3/4ton

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Okay, lol great, you did better than most Ive seen with a 36 gal tank. You got another 20 miles out of it and still aren't touching the other remaining three gallons. OP still isnt missing much at 31 vs MAYBE 33. Now it OP had a 26 gal tank that would be a different story.....

I've not run my tank below 1/4 tank but noticed the same thing DTE never shows anything over 700, highest I have seen was 660. Is it possible the truck does not know what size tank it has?
You can check you tank size in Forscan, I will have to find again where the size refence is located....

I think it calcs off your last average MPG, like if I do a tank in the city the next will show 450, and if I do a full tank highway it'll show 600. Ive stopped worry about the DTE until the gas light come on. I'm at 12k miles now and mines generally pretty accurate. Ive gotten down to 12 miles to empty and put in just under 25 gals (26 gal tank), so it builds in some kind of reserve still in all tank sizes.
 
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UGADawg96

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If there are any concerns between the 30 and 36 gal tanks for road trips or when towing, just buy a 5gal jug and bring it along. Otherwise, 30gal is more than enough.
 

jhohn

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Just bought a 2022 F150 3.5L Ecoboost, with max tow package. Sticker said "EXTENDED RANGE 36GAL FUEL TANK". Drove vehicle until it warned me "50 miles until empty", then a few more miles, then filled up. ONLY TOOK 27.5 gallons (my mileage, per the trip readout, and also determined by dividing my miles driven by 27.5, was 17.3 MPG).
Therefore with a 36 gallon tank I should have had another 147.05 miles (36-27.5=8.5, times 17.3=147.05).
So, either I was somehow given the 30.6 gallon tank, or the "50 miles until empty" calculation is wrong.
I reported this to the dealer I bought it from, and they told me another customer came in last week with exactly the same problem, and the issue is being reported to Ford.
In the state of California (and probably almost everywhere), it's illegal to sell a vehicle which doesn't match the sticker specifications, so if in fact the tank is only 30.6, Ford is on the hook for a full refund or a new tank, I would assume. Talking to an attorney about this today just to get my ducks in a row.
 

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hotrodmex

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I think the reserve on the 36 gallon tank is just really large.

I had to weigh out my truck for bringing it into CA and I got as detailed on the weight as I could when doing the weigh in. I drove it down to 50 mi DTE and weighed it without me in the truck. Separate weights were checked before they went back into the truck, but the gas was calculated from the known weight of gasoline. Weigh station was at a truckstop, so I filled immediately.


Tare weight (7 gal gas [42 lbs], running board brackets only, no spare/jack)4940
29 gal gas174
Running boards (no brackets)23.5
Jack + kit10.5
Spare tire61
Base Curb Weight5209

GVWR 7150 lbs - 5209 lbs base weight = 1941 lbs payload measured.

Sticker says 1948.

Considering the issue of the 36 gal tanks leading to fueling issues on steep inclines when low, I wouldn't be surprised it has a large reserve.

I mean, you can physically see the size of the tank, and how different the 30 gal and 26 gal tank looks. No need to guess.
 

jhohn

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Are you saying that even though the "50 miles until empty" is displayed, I actually have 8.5 gallons in the tank? Because it would only take 27.5g and I was getting 17.5 MPG (from both trip display and by manual calculation using the gallons it took and miles driven)..?
So if that's the case, is the display incorrect?
 

hotrodmex

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Are you saying that even though the "50 miles until empty" is displayed, I actually have 8.5 gallons in the tank?
Yes. Based on the weights that I observed, with similar conditions, it pencils out.

The IPC is configured for Distance Based Algorithm for the LFR DTE Level Configuration. At 50 mi doing about 20 MPG it would leave me with 4.5 gal at 0 DTE, which is a large, but I think reasonable reserve capacity. For you it would have been 5.5 gal reserve, but it also is an algorithm based on expectation. With how large the floor of that tank is, that is functionally empty if you go down a moderately inclined driveway. Look at where the fuel pump is.

Ford F-150 Upgrading to larger fuel tank 2021 F-150 1665539008489
Ford F-150 Upgrading to larger fuel tank 2021 F-150 1665539040890

There is some modding you can do to get the gauge to read how you want it to: https://forscan.org/forum/viewtopic.php?f=16&t=14698
https://www.f150forum.com/f129/fuel-tank-swap-forscan-adjustments-511630/#post7063148

Plus, Like I said, you can just got LOOK at the tanks. The idea that Ford has undersized the tank is a non-starter.

I also think expecting the gauge to literally go to zero on a consumer product where that means someone stranded on the side of the road is a weird expectation.
 

jhohn

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How does it pencil out?
The warning says "50 miles until empty". My mileage as reported by the truck, AND as calculated by me using miles driven divided by the gallons of gas it took on fillup, was 17.5 MPG. Only 27.5 gallons could be put into the tank at that time. Therefore if the tank is really 36 gallons, as it says on the sticker, then I had 8.5 gallons of gas still in my tank at fill-up. 8.5*17.5=148.75 miles. So why exactly is the truck telling me I'm going to be empty in 50 miles if I'm really going to be empty in 148.75 miles?
Essentially ,what good is that warning if it's off by a factor of 100 miles? How does one ACTUALLY KNOW when the truck will run out of gas?
The traditional use and meaning of a fuel warning light, is that you're about to run out of gas. What you're saying is, Ford has changed this meaning to: "If you had a 30.6 gallon tank, you'd be about to run out of gas (in 50 miles); however, you're not about to run out of gas, because, you have an additional 5.4 gallons of gas, so... just kidding"..
What the heck?
 
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air2mag

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I pull a horse trailer regularly so my empty is 1/4 of a tank. I think that’s why it’s called a fuel gauge and not a fuel indicator. It’s just an estimate.
 

jhohn

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I went back and re-read your last post. If I understand it, you're saying that the last few gallons (in my case, 5.5 gallons) may not be useable by the truck if I am going downhill? Is that correct?
Re: the dealer, he's had multiple people reporting the problem and wants me to bring my truck in, but he's a long distance away, and I'd rather gather info in case I don't have to make the trip!
Thanks for you help, BTW.
Update: I read the FORSCAN link, and the short answer may be that my truck THINKS it has a smaller tank than it actually has, and that FORSCAN will allow me to inform the truck of its actual tank size.
 
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boo radley

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The only fuel tank available with Powerboost is the 30.6 gallon tank. The larger 36 gallon tank won’t fit, the hybrid battery is in the way, so retrofit is out of the cards. You probably won’t find the difference that dramatic, the 36 gallon tank currently has a 5-ish gallon effectively unusuable portion and your Powerboost should net you better fuel economy than your previous trucks.
 

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