Fuel Mileage Being Miscalculated
12-08-2016, 06:56 AM
#21
Senior Member
Since the computer measures actual fuel used you may find it hard to believe it is more accurate then you think and your calculations could be the one in error. Since you can not be sure your fill the tank to the exact same level when you fill the tank-- unless you fill it to the top and can see the gas coming out, compensate for temperature and fuel density, or be sure your odometer is exactly right-- tire size and wear will effect this there is no way to really calculate your fuel mileage using the ole fuel used divided by the miles method. The odometer will also effect the computer calculation but the metered fuel will be exact used-- as a result the computer should be closer to actual mileage when compared to hand calculations. --for example a different pump could "click off" at different levels in the tank- assuming it is close 1/2 gallon off-- could effect your mileage a mile or two depending on miles driven.-- 200/10 is 20 MPG and 200/10.5 is 19 MPG-- the truth lies somewhere between the two --just saying
12-08-2016, 07:28 AM
#22
There also has to be a factor in the equation for either speed or RPMs vs transmission gear to determine how far you are going per metered fuel. A tremendous amount of room for error or estimation in all those calculations.
My bet is 95% accuracy for both hand and computer calcs should be acceptable and achievable.
12-08-2016, 09:14 AM
#23
Senior Member
I have used a Scangage Since it was first released. I still have the original, and have a Scanguage II that has been updated once in the last 8 years.
Even after adjusting the accuracy after each fill up, I usually see a difference of .2-.5 from what the unit predicted the fill up amount would be.
I use the same station, same pump, and try to fill up every Sunday morning.
On long trips I have had the difference in the pump indicated, and the scanguage to be off as much as a half a gallon. It makes me think that some way some how, gas stations have figured out how to control the "allowable error" to their favor.
The only way to be more accurate is to drive a known course of an exact distance, removing all variables, so tire pressure, tire wear, and even turning that can effect the odometer reading.
Just use the on board information for comparison of driving habits; i.e. towing or not. If you want a truly accurate measurement, buy an after market unit, understanding that it will also have limitations.
Even after adjusting the accuracy after each fill up, I usually see a difference of .2-.5 from what the unit predicted the fill up amount would be.
I use the same station, same pump, and try to fill up every Sunday morning.
On long trips I have had the difference in the pump indicated, and the scanguage to be off as much as a half a gallon. It makes me think that some way some how, gas stations have figured out how to control the "allowable error" to their favor.
The only way to be more accurate is to drive a known course of an exact distance, removing all variables, so tire pressure, tire wear, and even turning that can effect the odometer reading.
Just use the on board information for comparison of driving habits; i.e. towing or not. If you want a truly accurate measurement, buy an after market unit, understanding that it will also have limitations.
12-08-2016, 09:34 AM
#25
Senior Member
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Ricktwuhk (12-08-2016)
12-08-2016, 10:10 AM
#26
12-08-2016, 10:18 AM
#27
But it doesn't measure actual fuel used.........there isn't a fuel flow meter any where on the truck. The most accurate way to calculate fuel flow on production vehicles is to back it out from measured AFR and speed density based or measured air flow. Then you still have to worry about what AFR you call 0 fuel flow, among other things. The AFR reported will never read 0, even when coasting in gear, which enables deceleration fuel shutoff.
12-08-2016, 12:39 PM
#28
Senior Member
But it doesn't measure actual fuel used.........there isn't a fuel flow meter any where on the truck. The most accurate way to calculate fuel flow on production vehicles is to back it out from measured AFR and speed density based or measured air flow. Then you still have to worry about what AFR you call 0 fuel flow, among other things. The AFR reported will never read 0, even when coasting in gear, which enables deceleration fuel shutoff.
12-08-2016, 02:36 PM
#29
I'm just wondering if anyone else has notice that the fuel mileage being reported by the computer does not match calculating the actual fuel mileage.
For example, at my last fill on my 2016 Lariat with the 3.5L EB, I put 25.01 gal. of fuel in and had 419 miles on the tank. This would be about 16.75 mpg but the computer reported I got 17.6 mpg.
I reset all mpg calculations and trip odometers when I fill up, so it is accurate for that tank. If it was close (+- 0.1) I wouldn't be too concerned but this was almost 1 mpg off. I have noticed this same problem with various differences on different tanks of fuel.
Would love to hear if it is just me or if anyone else is experiencing similar issues.
For example, at my last fill on my 2016 Lariat with the 3.5L EB, I put 25.01 gal. of fuel in and had 419 miles on the tank. This would be about 16.75 mpg but the computer reported I got 17.6 mpg.
I reset all mpg calculations and trip odometers when I fill up, so it is accurate for that tank. If it was close (+- 0.1) I wouldn't be too concerned but this was almost 1 mpg off. I have noticed this same problem with various differences on different tanks of fuel.
Would love to hear if it is just me or if anyone else is experiencing similar issues.
My log on my 'stang http://www.fuelly.com/car/ford/musta.../ilkhan/383365
and I keep the indicated number in the comment for each fill up. Its always off.
12-08-2016, 02:42 PM
#30
My old Silverado was off by almost exactly 1mpg and my 2013 F150 is off by about .8 mpg, it's just the nature of the beast, it still gives you a goal, get as high as possible.