Mileage Computation
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2nd Gear
Joined: Jul 2019
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Mileage Computation
My 2018 F-150 Super Cab base 6 cylinder engine.
The question requires setup.
The onboard fuel mileage calculation is generally only about 1/2 mpg high, except after May of this year. I started topping the tank off since the price was so cheap and I didn't want to miss out. This evidently upset the computer as it would increase the range each time I refilled. Over several toppings, the stated range went from about 725 to 880 miles. And mpg went up from about 19.5 to almost 22 at one point. Which of course wasn't correct.
Does anyone definitively know how the pickups computer determines the amount of gasoline put into the tank and how it determines fuel usage? I had thought the computer would simply use throttle position to estimate fuel usage, but don't understand why the stated range and mpg went up.
I've stopped topping the tank off and fill it only when low (below 150 miles remaining) and the computed mpg is going back down toward 20. And the range is decreasing.
The question requires setup.
The onboard fuel mileage calculation is generally only about 1/2 mpg high, except after May of this year. I started topping the tank off since the price was so cheap and I didn't want to miss out. This evidently upset the computer as it would increase the range each time I refilled. Over several toppings, the stated range went from about 725 to 880 miles. And mpg went up from about 19.5 to almost 22 at one point. Which of course wasn't correct.
Does anyone definitively know how the pickups computer determines the amount of gasoline put into the tank and how it determines fuel usage? I had thought the computer would simply use throttle position to estimate fuel usage, but don't understand why the stated range and mpg went up.
I've stopped topping the tank off and fill it only when low (below 150 miles remaining) and the computed mpg is going back down toward 20. And the range is decreasing.
Moderator
Joined: May 2005
Posts: 8,232
Likes: 1,248
From: San Antonio, TX
Welcome to FTE Larry.
Another thing you can try is to adjust the AFE bias. You can access that by putting your truck in diagnostic mode. Turn your key on without starting and press the OK button on your steering wheel or your trip reset button until the diagnostic mode shows on your dash. Scroll to AFE bias and adjust by trial and error.
Another thing you can try is to adjust the AFE bias. You can access that by putting your truck in diagnostic mode. Turn your key on without starting and press the OK button on your steering wheel or your trip reset button until the diagnostic mode shows on your dash. Scroll to AFE bias and adjust by trial and error.
Lead Driver
Joined: May 2015
Posts: 5,889
Likes: 360
From: Mts. S. of San Francisco
I don't know for sure, but the throttle is probably not how the computer calculates fuel usage. The most accurate way would probably require a flow transducer in the fuel line, but that is probably more expensive than Ford would want to spend. More likely, it counts the number and volume of the "squirts" that go into each combustion cycle for each cylinder. That's likely a fairly accurate way to measure fuel flow.
Lead Driver
Joined: Jun 2005
Posts: 8,475
Likes: 728
From: Calgary Canada
Yes, the number and length of "squirts" is probably how they do it, since that's something the computer would already know, and should be accurate within a couple percent I'd think, which is about as close as anything. I wouldn't want to crack into diagnostic mode unless the truck was running badly.
Moderator
Joined: May 2005
Posts: 8,232
Likes: 1,248
From: San Antonio, TX
It’s just a test mode. You see a lot of variables there in real time. Temps, RPMs, volts etc. a lot of the same info that a Scangauge gives. That only thing you can adjust is the AFE bias.
Lead Driver
Joined: Jun 2005
Posts: 8,475
Likes: 728
From: Calgary Canada
Huh, I had no idea. Learned something today I guess. Thanks.
Lead Driver
Joined: Jul 2004
Posts: 5,947
Likes: 63
From: in the woods of MA
The fuel usage should be fairly easy to calculate. The more interesting question I think is how do they determine how much fuel was put in the tank? Just by the gauge mechanism? Is it that accurate?
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Fleet Mechanic
Joined: Sep 2016
Posts: 1,801
Likes: 48
From: Abilene TX.
How much is in the tank just like you do by the fuel gauge, which is just an estimate by volume of the tank and the float level. To have a better idea it would have to be manually entered by the person who filled it down to 100ths of a gallon every time. the computer knows by length of time the injector is open how much fuel by volume is sprayed . dirty injector less full O2 sensor shows lean mixture. computer holds injector open longer so it thinks it is using more fuel. These vehicles can so so much more now days and with computers it seems like people what absolute values. Well folks it still isn't going to happen Fuel has been gauged the same way with a few refinements since the electric gas gauge was invented. It now uses milli-amps instead of amps.it still uses a float and if you put the exact amount of fuel in 4 vehicles park each with a different front back left or right side high or low you will get 4 different fuel levels the computer will give 4 different estimates on miles to empty.
OK off my soap box now.
TJ
OK off my soap box now.
TJ
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Joined: Jun 2006
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From: Ottawa, Ontario
My 2018 F-150 Super Cab base 6 cylinder engine.
The onboard fuel mileage calculation is generally only about 1/2 mpg high, except after May of this year. I started topping the tank off since the price was so cheap and I didn't want to miss out. This evidently upset the computer as it would increase the range each time I refilled. Over several toppings, the stated range went from about 725 to 880 miles. And mpg went up from about 19.5 to almost 22 at one point. Which of course wasn't correct.
The onboard fuel mileage calculation is generally only about 1/2 mpg high, except after May of this year. I started topping the tank off since the price was so cheap and I didn't want to miss out. This evidently upset the computer as it would increase the range each time I refilled. Over several toppings, the stated range went from about 725 to 880 miles. And mpg went up from about 19.5 to almost 22 at one point. Which of course wasn't correct.
The recommended tank refilling procedure is to stop when the gas pump shuts off and not overfill as this can flood the evap system with raw fuel.. which isn't good. But more fuel in the tank means more range to empty too. Fuel consumption calculations are based on how much fuel the injectors are spraying into the engine and should be quite accurate, but this number will vary constantly depending upon driving habits, environmental conditions(temperature and elevation), and fuel grade used which happens twice a year for many whether we like it or not when winter gas is introduced and discontinued in the fall and spring.
Lead Driver
Joined: May 2015
Posts: 5,889
Likes: 360
From: Mts. S. of San Francisco
That is probably a valid considerations. I don't know how a full tank is computed, but I would imagine that when the computer sees the tank has gone from a 1/4 tank to "full", it bases the calculation on how much it thinks is in the tank, and computes based on what a full tank is. A full tank that changes volume can not help. So having a consistent point at which the tank is full would be a step in the right direction.
Elder User
Joined: Aug 2005
Posts: 536
Likes: 5
From: Phoenix, AZ
My 2018 F-150 Super Cab base 6 cylinder engine.
The question requires setup.
The onboard fuel mileage calculation is generally only about 1/2 mpg high, except after May of this year. I started topping the tank off since the price was so cheap and I didn't want to miss out. This evidently upset the computer as it would increase the range each time I refilled. Over several toppings, the stated range went from about 725 to 880 miles. And mpg went up from about 19.5 to almost 22 at one point. Which of course wasn't correct.
Does anyone definitively know how the pickups computer determines the amount of gasoline put into the tank and how it determines fuel usage? I had thought the computer would simply use throttle position to estimate fuel usage, but don't understand why the stated range and mpg went up.
I've stopped topping the tank off and fill it only when low (below 150 miles remaining) and the computed mpg is going back down toward 20. And the range is decreasing.
The question requires setup.
The onboard fuel mileage calculation is generally only about 1/2 mpg high, except after May of this year. I started topping the tank off since the price was so cheap and I didn't want to miss out. This evidently upset the computer as it would increase the range each time I refilled. Over several toppings, the stated range went from about 725 to 880 miles. And mpg went up from about 19.5 to almost 22 at one point. Which of course wasn't correct.
Does anyone definitively know how the pickups computer determines the amount of gasoline put into the tank and how it determines fuel usage? I had thought the computer would simply use throttle position to estimate fuel usage, but don't understand why the stated range and mpg went up.
I've stopped topping the tank off and fill it only when low (below 150 miles remaining) and the computed mpg is going back down toward 20. And the range is decreasing.
There was a spike where the lie-o-meter showed a much higher miles to empty. After I re-filled later in the month, my spread sheet where I keep all of the milage milage stats showed 34.5 mpg for the last tank. The best I had ever seen over 3yrs has been 22mpg.
But after 3yrs Trip 2 which I never reset shows an avg 17.1. My spread sheet also shows 17.1.
Its really on the money and that is with NO adjustments.
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