calculated vs. computer MPG - Please post your results

How is it based on past MPg?? U make no sence. We have an Audi and when u fill the tank up it tells u that u have like 540 miles on ur full tank. We have a Lexus also and when u fill up the tank it tell u how many miles u have till an empty tank. Same as the prius. When u fill it up and hit the button on steering wheel the trip button I believe. And hit that button till it says u hVe *blank miles* till empty tank. It should almost be the same Everytime u fill up. Of course it may be different from ur way of driving. But it tell u how many miles u have till u go empty. That's how u know hey it's time to fill up!!!! when I would fill up my tank before the update it would say about 525 miles when the tNk was full. And of course I could always achieve more depending on my driving. Now with the update and I fill my tank and it says now 420 or less on a full tank and I don't even get that many miles on my prius I get about 380 on a full tank. This sucks and is bullshit. And they keep telling me there's nothing wrong with I t. Someone just relied to my post and said when they fill up there tank there meter reads out 600 miles on a full tank till next fill up!!!!

 

Simple mathematics:

1) MPG = MILES / 11.9 gallons.

2) To "estimate" MILES, MPG must be known "...a priori..." which the ECM assumes to be equal to your LAST MPG value, which unfortunately is NOT a wholly accurate assumption. For example, yesterday you drove in the city (poor MPG) before filling-up, but tomorrow you will drive on the freeway (good MPG)...they're totally different MPG conditions.

...hence:

3) MILES(est.) = 11.9 gallons(known) × MPG(est.)

 

I'm not trying to figure out the mpg. I know how to get mpg. And when I calculate the mpg I'm getting like 33mpg and the computer tells me it's like 35mpg. It's stupid I'm not getting good mileage ever since the update.

im not asking what everyone's MPg is. I'm asking when u fill ur tank up. The computer resets and tell u that u have let's say 500 miles on a full tank. That's what I want to know. When I fill my tank up 11.9 gallons it says I have 380 to 420 miles on that tank. Till it becomes empty. But I know it will very u might get more if u drive good or less if ur driving conditions aren't good... Got that part. Not sure if we're understanding each other.
I had a Honda civic before that stupid car got about 340 miles - 360 miles on a full tank and had more gallons I believe then the prius!! How I'm I getting the same shit miles per gallon as a civic when I have a prius. ???

Everyone is saying they can get over 500 miles and up to 600 miles. And I get 380 most of the time... This has been happening ever since the update. I'm not the only one that there mpg has dropped since the update on the computer. I keep hearing it dropped for everyone from 8 to 10 mpg. Wth!!! Toyota!!!

 

Like I've stated before, the ECM is using its last-known MPG value (which in your case sounds to be 33-38 MPG) when it "forecasts/estimates" the MILES-to-empty for the newly refilled tank.

I vaguely recall seeing numbers like 480-500 miles for our 2014 Prius-4, but this is NOT a number I value worth recording.

 

My last fuel up, 54.7 fuelly, 57.9 display, 5.85%

 

I got 72.5 MPG displayed in the dash, while 68.8 MPG in fuelly. 5.4% different.

 

Double post.

 

My last tank I got 48 according to the display. Actual was 45.5.

The difference for me is usally 2.5-3.0 mpg. Pretty consistently.

 

Here in Australia, saw 4.9L/100km on the computer, and 5.2L/100km on the tank. However, I think the majority of this error is the speedometer calibration - which is about 5% out (too fast) when compared to GPS measurement.

Anyone know about calibrating the speedometer? Maybe my tires are slightly smaller diameter... not sure.

 

Hey buddy,

I'm getting a little less than what the computer says out on the "distance to empty" reading. Need to take a long-term approach to this though, as it's heavily influenced by your driving, number of starts, temperature etc... Run the Trip B for each fill and compare it to the start each time.

 

Speedometer is required to read a bit high, by law. The car's fuel economy display is in no way tied into the speedo.

 

If you use the distance from the dash than the speedometer error as no consequence on the mpg offset

 

CORRECT!

I am finding the indicated mileage tracks the speedometer error.

Bob Wilson

 

Hmmm... this is an interesting topic.

I can see a few people have posted that the speedometer doesn't affect your distance or mileage, however I don't understand the logic. The only way the computer (ECU) knows how far the car has driven is from integrating the the speed signal over time - there's no other signal that the ECU can use.

From what I understand, the speed is just derived by your main wheel RPM - there's no GPS-signal in the car. I have a basic model, so the GPS speed I'm quoting is coming from a non-integrated aftermarket Garmin.

Any thoughts on this?

 

I have been told that despite the laws requiring the speedometer to read slightly more than your actual speed, the computer knows your actual speed and does the calculations for mileage with that rather than the direct reading from the speedometer. Thus the only reading affected by this "error" is the reading on the speedometer.

 

Usually I get ~520 "till next fill up". Although today I filled up to the top, literals: gas level visible in the opening. But it said 451 till fill up...

While I am on it: after the alarm of "Empty !" on gas I can drive 150-130 ml. Which corresponds with traditional empty mark when ~2,5 Gal is still in the tank.

 

Unless you have a filled 2 gal. gas can in the back, I'd not test how far you can go past the "E".

The system is set up to protect people from themselves.

 

mpg/tank average overall incar- what each tank shows in car
MPG/Tank
52.644 52.644
54.498 53.571
55.142 54.095
55.546 54.457 58.2 in car
56.696 54.905 58.6 in car
57.009 55.256 57.3 car/60.1 tank
58.791 55.761 57.7 car/60.2 tank
56.314 55.830 58.0 car/60.0 tank
57.745 56.043 58.1 car/59.7 tank
57.483 56.187 58.4 car/60.6 tank
58.607 56.407 58.5 car/59.6 tank
56.107 56.382 58.5 car/59.6 tank
59.110 56.592 58.8 car/61 tank
55.805 56.535 58.9 car/60.3 tank
54.634 56.409 58.8 car/58.2 tank
56.913 56.440 58.9 car/59.8 tank

 

Whoa! Too many numbers to look at before my morning coffee.

 

Seems like I am on the rare here.

My dash was reading 54.5mpg but when I calculated on my fill up I calcuated 56.3

Filled up at 468 miles driven from full tank and filled up 8.312 gallons.