How accurate is gas guage?

[DIYAndy]

I have been using the spreadsheet/pdf below on my gas tank and it's fairly accurate

Notes:
a. Vehicle: Gas mileage for my "plain Jane" 2019 Ford Ranger XL 4x2 supercab/extended cab with 6' bed started
out with ~ 16 MPG with only 33 miles on it. After 250 miles the MPG jumped to ~ 20 MPG for all city driving.
b. 2019 Ford Ranger XL rated MPG: 21 city - 26 highway and average 23.5
c. Ranger break-in period needed: ~ 2000 miles - for true gas mileage MPG

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[Johnpenn]

Has anyone tried or would recommend running out of gas with a spare 5gal can in the bed to see how much reserve is actually there or accidently? I know one person ran within a couple of tenths of empty and running out isn't recommended. I am guessing each truck is a little different because of gage variation and it is good to know.

 

[DIYAndy]

I am guessing each truck is a little different because of gage variation and it is good to know.

From what I have seen - full to empty is 17 gallons and with a reserve of 1.8 gallons for a total 18.8 gallons. At the 1/4 level which alarms low level at 50 miles to empty - by subtracting the reserve at the 1/4 tank level works out to be ~ 50 miles (very close to it without counting the reserve)
Inspect XL_Gas_R1.pdf (above)
The calculated/estimated miles to empty also confirms my numbers
Of course, needless to say that MPG vehicle performance will vary from vehicle to vehicle along
with the driving habits of the driver
As for the vehicle gas gauge being accurate - I would have to say it is very accurate. IMHO

 

[DIYAndy]

Just curious - forum members how many gallons does it take you from different levels to fill up?
3/4 full to full tank? (4.25 gal)
1/2 full to full tank? (8.5 gal)
1/4 full to full tank? (12.75 gal)
Empty to full tank? (17.00 gal)
(EMPTY does not include the spare reserve!)

BTW - I taped the above numbers on the back of a $1 battery/solar calculator, from Walmart, for easy
pre-paid gas totals.

 

[P. A. Schilke]

Okay Folks,

Here is the deal....bad idea to run out of gas. The warning is calibrated so it gives you a sense of urgency before actually running out of gas. One of the reasons is that running out of gas leans out the engine and exhaust temps rise and catalyst can be damaged or fuel pump damage may occur in the in tank pump....so the calibration is purposely designed to make you fill up before running out of fuel. It is very foolish to try to stretch it out or gamble you can make it...Please, stop and throw a couple gallons into the tank if that is all you can do...

best,
Phil Schilke
Ranger Vehicle Engineering
Ford Motor Co. Retired

 

[P. A. Schilke]

Hi Folks,

By the way, there are quite a few fuel systems tests that are run on the prototypes. There is more than just packaging a tank between the frame rails and the driveshaft. You may be interested that the development engineers run a series of tests around adding one gallon of fuel to a dry tank...the vehicle has drains installed in the tank and the tank is drained, the engine is started until it runs out of fuel, then the one gallon of fuel is added to the tank and the vehicle started and idled for a set period of time.

Then the vehicle is placed on a ramp of around 10°, nose up and the procedure is repeated. The vehicle is then clocked around in 45 degree increments on the ramp and again the procedure is repeated. This is a total of 9 tests of running out of fuel. This is then repeated again for a vehicle fully laden to GVW, making a total of 18 test points....If the vehicle fails any of the tests, it is back to the drawing board to redesign the tank or fuel pickup or both. I recall that the 1985½ Aerostar proved difficult to meet the requirements but finally, they figured out what to do to make it pass the tests.

best,
Phil Schilke
Ranger Vehicle Engineering
Ford Motor Co. Retired

 

[jh13]

I ran it down to five miles yesterday and put 17.7 gallons in. So it seems pretty close to at least the rated capacity, unsure what the actual capacity is though.

 

[THLONE]

Did they also inspect the fuel pump after the tests to see what damage to it was done?

 

[DIYAndy]

Here is the deal....bad idea to run out of gas

So, P. A Schilke - do the following fuel gas tank levels seemed reasonably close?
The only difference in gas tank readings are one's eyesight in determining the gas level.

Fuel levels required back to full tank
3/4 full to full tank? (4.25 gal)
1/2 full to full tank? (8.5 gal)
1/4 full to full tank? (12.75 gal)
Empty to full tank? (17.00 gal) - --one user said 17 another said 17.7
(EMPTY does not include the spare reserve!)

Full to empty is 17 gallons and with a reserve of 1.8 gallons for a total 18.8 gallons.
1/4 level which alarms low fuel level at 50 miles to empty.

 

[dmeyer302]

@P. A. Schilke Your development stories will never get old, please share often!

 

[MSG W]

Hi Folks,

By the way, there are quite a few fuel systems tests that are run on the prototypes. There is more than just packaging a tank between the frame rails and the driveshaft. You may be interested that the development engineers run a series of tests around adding one gallon of fuel to a dry tank...the vehicle has drains installed in the tank and the tank is drained, the engine is started until it runs out of fuel, then the one gallon of fuel is added to the tank and the vehicle started and idled for a set period of time.

Then the vehicle is placed on a ramp of around 10°, nose up and the procedure is repeated. The vehicle is then clocked around in 45 degree increments on the ramp and again the procedure is repeated. This is a total of 9 tests of running out of fuel. This is then repeated again for a vehicle fully laden to GVW, making a total of 18 test points....If the vehicle fails any of the tests, it is back to the drawing board to redesign the tank or fuel pickup or both. I recall that the 1985½ Aerostar proved difficult to meet the requirements but finally, they figured out what to do to make it pass the tests.

best,
Phil Schilke
Ranger Vehicle Engineering
Ford Motor Co. Retired

I appreciate you insight and I bet you have some great design stories....

 

[P. A. Schilke]

Hi Folks...

Yep...tons of design stories that some would boggle your mine...Ripped the rear axle out of a $2 million prototype Windstar....what a disaster....turned out to be a CAE mistake of analysis with a 1lb rear axle...Took my guy about day and half to find this huge error...proper weight was 125lbs... All the prototypes had to be reworked with much thicker brackets than the tinfoil ones originally installed... Even the old timers at the test track had never seen anything like this....

Phil Schilke
Ranger Vehicle Engineering
Ford Motor Co. Retired

 

[P. A. Schilke]

So, P. A Schilke - do the following fuel gas tank levels seemed reasonably close?
The only difference in gas tank readings are one's eyesight in determining the gas level.

Fuel levels required back to full tank
3/4 full to full tank? (4.25 gal)
1/2 full to full tank? (8.5 gal)
1/4 full to full tank? (12.75 gal)
Empty to full tank? (17.00 gal) - --one user said 17 another said 17.7
(EMPTY does not include the spare reserve!)

Full to empty is 17 gallons and with a reserve of 1.8 gallons for a total 18.8 gallons.
1/4 level which alarms low fuel level at 50 miles to empty.

Hi Andy,

Those numbers are probably pretty good to use for day to day driving. I do not have access to the exact numbers used by fuel systems engineering as all my friends at Ford are also retired....you have a pretty good handle on this and I would recommend others to use your experimentally determined gallonage! Good Job!

best,
Phil Schilke
Ranger Vehicle Engineering
Ford Motor Co. Retierd

 

[P. A. Schilke]

Did they also inspect the fuel pump after the tests to see what damage to it was done?

The short answer is no. The reason is that the fuel pump is tested in the Fuel Systems Lab under laboratory test conditions. At the end of the test, we replace the whole sending unit and pump as other departments will need the prototype vehicle for their work.

By the way....If you ever need to replace the pump...it is far easier to pull the pickup box than to drop the tank... Remove the box to frame bolts. Pull the filler neck.. and disconnect the evep lines .UNDO THE FRAME TO BOX WIRING HARNESS (caps for emphasis as this can be a big wooops!) remove the tailgate and then you and a friend pick up the box and set it behind the vehicle....Now the top of the tank has full access.

Best,
Phil Schilke
Ranger Vehicle Engineering
Ford Motor Co. Retierd

 

[PNW_Ranger87]

By the way....If you ever need to replace the pump...it is far easier to pull the pickup box than to drop the tank... Remove the box to frame bolts. Pull the filler neck.. and disconnect the evep lines .UNDO THE FRAME TO BOX WIRING HARNESS (caps for emphasis as this can be a big wooops!) remove the tailgate and then you and a friend pick up the box and set it behind the vehicle....Now the top of the tank has full access.

Best,
Phil Schilke
Ranger Vehicle Engineering
Ford Motor Co. Retierd

Well obviously I hope that I never run into this but if I do I'll be very glad I saw this post. I'll have to permanently engrain this into my mind for future use! As always, I appreciate the insight!

I'm also in the, as soon as it hits 50mi DTE I try to fill up immediately, group. I have only put 500 miles on my truck and this is only my second fill up but I was definitely curious when I got to "1/4 tank" and the 50mi DTE light came on. I'm used to the light showing just before it hits the last line before going into the red. I came here to see if anyone else has this same readout from the gauge and it looks like that is the case. I was thinking that the calibration would adjust over time but it seems that I'll just have to get used to knowing that "1/4 tank" doesn't actually mean 1/4 tank. I know it would only really represent about 50-60 more miles (depending on gas mileage) if it was actually 1/4 tank left so I guess this is a nice EARLY warning to get fuel.

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