F150 dash mpg doesn’t match real world. Why?

[hebelr]

Hi, I have just started using Fuelly and am very disappointed with its findings. My trucks dash estimates are way off the actual mpgs. I added larger street tires to try and change my axle ratio. My truck cam with real low gearing because it’s a heavy payload package. I then purchased a speedo recalculator to adjust my dash mpgs to be correct again. I know the odometer and my speedo are now correct because I checked it on a 200mile trip with gps. On my last fuelly entry my truck said 21mpgs for the whole tank, then fuelly said it actually was 18.7. I am just wondering if anyone else has had the same problem.

[Draigflag]

Perfectly normal, your dash reading is just a rough estimate, mine is on average 3.5 mpg optimistic than actual. This is the case with 99% of vehicles dash readouts, so don't assume yours is any different.

[JockoT]

I log the actual calculated mpg (Fuelly), the reading my ScanGauge E displays, and the on board computer's figure. They are all different. Usually only about 2 mpg difference, but sometimes as much as 4 mpg. The on board unit only counts the injector pulses from the engine ECU and about once every 10 seconds does an average computation which decides the number it displays. The smoother your driving the nearer the true figure it gets, but it is still just an estimate.

[JohnnyJeep]

New to Fuelly haven't even filled up yet to start using it, but I've always kept track of my miles and mpg. Even tracked the fuel on vehicles that showed it. It was always wrong, but consistent. Even though it was wrong, was able to see what habits or conditions were effecting my mileage. More important, when the readout suddenly changes, I instantly knew there was probably a problem somewhere.

[JockoT]

Agreed. My ScanGauge E shows me average mpg as well as instantaneous mpg (on board display on my model only gives average between resets). It is not spot on but near enough to show trends and any anomalies, such as results from a binding brake or slow puncture.

[hebelr]

Thanks for the input. I will now see if I can get my truck into actual 20mpgs average.

[cdlamb]

There is a way to change the display readout to more accurately reflect actual fuel consumption on F150. I Believe you need to press, and hold the OK key on the left hand side of steering wheel , then turn key on, (Not Starting) continue to hold. There is a test function you can scroll through, with radio outputs, etc. From there you can tab through until a fuel bias, which will be set stock at 1000. If you adjust it down to around 957 I believe is where mine is at it seems closer. I didn't find any other settings that could be changed, or screwed up.

[dgcamero]

Originally Posted by cdlamb

There is a way to change the display readout to more accurately reflect actual fuel consumption on F150. I Believe you need to press, and hold the OK key on the left hand side of steering wheel , then turn key on, (Not Starting) continue to hold. There is a test function you can scroll through, with radio outputs, etc. From there you can tab through until a fuel bias, which will be set stock at 1000. If you adjust it down to around 957 I believe is where mine is at it seems closer. I didn't find any other settings that could be changed, or screwed up.

Do you know how to do that for a Nissan NV200? It drives me nuts for it to be off in my work van!

[genesound]

Odd, my 2007 Jeep Grand Cherokee MPG is spot on, always has been. MPG on dash and actual MPG agree to the point of the error being undetectable. I have a Linear Logic ScanGauge II gauge on the JGC too. It's way off, but there is a way to calibrate the ScanGauge. I don't bother since the Jeep's MPG gauge is so accurate. I use the ScanGauge for other readouts, like water temp, voltage, Digital MPH, RPM, reading and clearing CEL codes and such. It's a handy gizmo, I keep it hooked up to the OBD2 port all the time.

[brent88]

on my last Fill up it was off by only 0.1MPG from average claimed 24.1 fill up was 24.04

only off by 0.06MPG or less then 1%


i did do another fill up after it was off by 4mpg from the average.

BUT i was pressed for time though so I was going faster then "normal".. 75-80 compared to my normal 59mph,..

my grandpa gave me some $$ for gas anyway so i paid zero out of pocket on that fill up