Hybrid MPG gauge too high by 5.6%

[MaverickDragon]

If you look again, you will see that I said 1.000 and not 1,000. (3 digits past decimal to imply precision on the pump display) The rest really is easy peezy if you have a scale and remember to measure the tare weight of the can before filling up. A thermometer and graduated cylinder will round out your gear to check pump calibration as well as the dept of weights and measures. If you want to measure the alcohol fraction as well, the process is really simple since alcohols are soluble in water but gasoline is not. The graduated cylinder does that too. We learn things from actually doing that armchair Googling can't teach.
Your comment on the compressibility of liquid gasoline under barometric pressure changes is interesting. Admittedly, it is twice as compressible as water, but really...?

I missed the decimal vs comma. My bad. I wasn't expecting 3 digits with a zero value.
A pump that displays values to 1/1000 of a gallon doesn't mean it's accurate, and no pumps used to dispense gasoline are anywhere close to that level of accuracy.

I attempted to note potential factors affecting volume, with temperature being primary, and pressure I agree is insignificant, but it's a nit, and you seem to like being thorough.

What seems lost in this now going way off topic conversation is that the weight of the fuel you measured is well within the normal range for 87 octane 10% ethanol fuel, which was noted, that can vary for all of the reasons previously outlined, even when the most precise measurements available are applied. The basic problem is you used an inaccurate weight to compare to.

Regardless of the effort and calculations made, you will only, at best, confirm a non problem.
I've got nothing more to add.

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[Glen Baker LLC]

I wonder how placement of gasoline storage tanks, affect the volume of gasoline when it's dispensed.?

Here in the west and southwest because of the amount of rock that may be in the ground some of our gas stations have above ground tanks. They are directly in the sun and in the cold.

Compare that with in the ground tanks. Wouldn't these tanks depending upon their depth dispense fuel at the same temperature year-round?

 

[HeyBales]

That's what I was going to mention.

That weighed gal at 6.15 lb was probably correct for the temp it was coming out at if underground tank.

 

[Timothyd]

In early October '24, I reset the trip monitor and started keeping detailed gas records. Tire pressure was checked/corrected each fill up. The monitor is consistently high for each fill up, by 3.4% to 6.1%.
After 5043 miles, the actual is 36.7mpg but the monitor shows 39.0, 5.6% too high. Anyone else notice this?
Is this intentional? Can it be adjusted to be more accurate?
I have a 2023 XLT Hybrid.

Mine was almost 2% high. Checked it when newer, haven't bothered since.

 

[MaverickDragon]

I wonder how placement of gasoline storage tanks, affect the volume of gasoline when it's dispensed.?
Here in the west and southwest because of the amount of rock that may be in the ground some of our gas stations have above ground tanks. They are directly in the sun and in the cold.
Compare that with in the ground tanks. Wouldn't these tanks depending upon their depth dispense fuel at the same temperature year-round?

Apparently no temperature compensation is built into the fuel pump delivery system, so that warmer fuel in a storage tank means you actually get less fuel than if you got cold gas.

With underground tanks there is very little variation in temperature.
An above ground tank on a hot day you could end up with less fuel, but then there the heat of the day that has to be overcome from the cold of the night before.

The standard reference temperature is 60 degrees F for gasoline,
Gasoline expands by approximately 0.0079 gallons per gallon when the temperature increases from 60°F to 80°F., so even if the fuel got that warm, a 15 gallon fill up would only be a difference of less than a pint.

BTW -
I've never seen above ground tanks in Arizona for gasoline.. Is that a Nevada thing?

 

[Glen Baker LLC]

Yes
Out in the wilds of Nevada. Think the middle of nowhere, which is pretty much all of Nevada.
Here's a picture of the above ground tanks when I was in Utah.

I've seen them in Arizona way south of Tucson probably 25 years ago, I don't remember where exactly.
I've seen them in Idaho too.

 

[Mavster Mechanic]

Above ground tanks seen in Alaska.
And anywhere they are too lazy to dig.

I think in the city they bury for lack of space. Temperature control is probably low on the priority list.

 

[MetalsGeek]

Mine was almost 2% high. Checked it when newer, haven't bothered since.

In early October '24, I reset the trip monitor and started keeping detailed gas records. Tire pressure was checked/corrected each fill up. The monitor is consistently high for each fill up, by 3.4% to 6.1%.
After 5043 miles, the actual is 36.7mpg but the monitor shows 39.0, 5.6% too high. Anyone else notice this?
Is this intentional? Can it be adjusted to be more accurate?
I have a 2023 XLT Hybrid.

Yes, you can manually tune your indicated MPG. Ford did this one right, but doesn't make it easy.
Enter Engineering Test Mode:
1. Depress & hold brake pedal.
2. Depress and hold the OK button on steering wheel.
3. Wait >5 sec, then insert key and switch ignition to "RUN" (OFF-ACCY-RUN-START).
4. Continue holding OK until green "ET" appears in dash display at top right. (~ 15 sec)
5. Use OK & MENU buttons to explore
6. AFE Bias is "Average Fuel Efficiency"; tune it to match your MPG. 1000=default, 970 reduces displayed MPG by 3%, etc. You would use 1000*367/390 = 941.
To start the engine, momentarily turn key to START and depress accelerator pedal (like usual). It took me a while to learn THIS little secret that's not in the user manual but should be.

 

[MetalsGeek]

Ya.

Measuring ONE gallon is not very accurate. How do you know you got exactly one gallon? Also, some evaporates by the time you put it on the scale. And how good is your scale? And how do you know?

The topic of conversation at that point was the accuracy of the pump at your local station, so the idea was to weigh your lawnmower gas can to get its tare weight, then buy what your local station's pump claims is 1.000 gallons. Weigh the can again and subtract its tare. This was all done to avoid measuring the volume of gas directly in a graduated cylinder, which would have saved a lot of typing! Of course, even this got complicated when people started to involve temperature compensation (NOT done in USA) or variation in gas blends as well as methanol fraction. I now have a 6 Kg digital scale that claims to resolve 0.01 grams, although it was not used when that thread started. Calibration is of course a valid issue and no, I did not buy the NBS certified weights with the scale. Then too, the nozzle drips more than the evap loss so we must not fool ourselves over precision. The ultimate goal (now lost in all the discussion) was to determine very simply whether the gas station was screwing its customers.

 

[rk06382]

Above ground tanks seen in Alaska.
And anywhere they are too lazy to dig.

I think in the city they bury for lack of space. Temperature control is probably low on the priority list.

To bury a tank is not cheap.

The EPA regulates buried storage tanks (Underground Storage Tanks, or USTs) under 40 CFR Part 280 to prevent and detect petroleum leaks. These federal regulations require USTs to have corrosion protection, spill prevention, and overfill prevention, alongside strict leak detection and periodic integrity testing.

 

[MaverickDragon]

To bury a tank is not cheap.

The EPA regulates buried storage tanks (Underground Storage Tanks, or USTs) under 40 CFR Part 280 to prevent and detect petroleum leaks. These federal regulations require USTs to have corrosion protection, spill prevention, and overfill prevention, alongside strict leak detection and periodic integrity testing.

My next door neighbor traveled all over the US doing just that and even back in the day, those tests weren't cheap.

 

[dochawk]

I get 26 mpg for a long term average from checking the old fashioned way.

Blindly believing the odometer?

The chain, owned by 7-11, blew me off. I have not bought anything from that chain since.

Your arteries, colon, and other assorted organs thank you!

 

[rk06382]

Blindly believing the odometer?





Your arteries, colon, and other assorted organs thank you!

I loved getting a 7-Eleven BIG-GLUP.

 

[MaverickDragon]

Ya.
Measuring ONE gallon is not very accurate. How do you know you got exactly one gallon? Also, some evaporates by the time you put it on the scale. And how good is your scale? And how do you know?

There are a lot of variables of varying significance.
The basic problem on this topic turn is that gas stations sell fuel by volume, not weight.
They sell a product but don't control the content.

The weight of a gallon of regular gasoline changes slightly with variables but the expected weight noted above at 6.33 pounds that a poster had a problem with is unrealistic.

Heavier fuel weight will happen when it's cold, or has more ethanol than less, or has more additives, or has some water contamination. Any or all of these factors will result in a measured quantity of fuel to to increase its weight. The reverse of these factors will make the fuel lighter.

There is no set weight that gasoline is expected to weigh beyond a range which can vary between 5.8 to 6.5 pounds. Expecting fuel weight o be a specific number, especially one that is on the upper end of the spectrum doesn't mean a gas station delivered less fuel than it should have.

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